Reapply "[libc++] Optimize num_put integral functions" (#131613) #133572

philnik777 · 2025-03-29T08:08:26Z

This reverts commit d1156fc.

This patch fixes the reported incorrect formatting changes and adds tests for them. The performance should be unaffected, since there are no significant changes required to fix the bugs.

Specifically, a > was changed to a >= to also add a + in the zero case, and we're checking for zero now before printing the octal and hexadecimal prefixes.

Closes #131710

llvmbot · 2025-03-29T08:09:03Z

@llvm/pr-subscribers-libcxx

Author: Nikolas Klauser (philnik777)

Changes

This reverts commit d1156fc.

This patch fixes the reported incorrect formatting changes and adds tests for them. The performance should be unaffected, since thee are no significant changes required to fix the bugs.

Patch is 73.10 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/133572.diff

17 Files Affected:

(modified) libcxx/docs/ReleaseNotes/21.rst (+8)
(modified) libcxx/include/__charconv/tables.h (+8-12)
(modified) libcxx/include/__charconv/to_chars_base_10.h (+14-18)
(modified) libcxx/include/__charconv/to_chars_integral.h (+45-27)
(modified) libcxx/include/__charconv/to_chars_result.h (+9)
(modified) libcxx/include/__charconv/traits.h (+3-7)
(modified) libcxx/include/__format/formatter_floating_point.h (+1)
(modified) libcxx/include/__format/formatter_integral.h (+1-1)
(modified) libcxx/include/__format/formatter_output.h (-18)
(modified) libcxx/include/locale (+65-39)
(modified) libcxx/include/module.modulemap (+4-1)
(added) libcxx/test/benchmarks/locale/num_put.bench.cpp (+39)
(modified) libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_long.pass.cpp (+173-118)
(modified) libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_long_long.pass.cpp (+182-118)
(modified) libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_pointer.pass.cpp (+9-13)
(modified) libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_unsigned_long.pass.cpp (+162-118)
(modified) libcxx/test/std/localization/locale.categories/category.numeric/locale.nm.put/facet.num.put.members/put_unsigned_long_long.pass.cpp (+162-118)

diff --git a/libcxx/docs/ReleaseNotes/21.rst b/libcxx/docs/ReleaseNotes/21.rst
index 877aa06f8b7e4..25e91c67d8139 100644
--- a/libcxx/docs/ReleaseNotes/21.rst
+++ b/libcxx/docs/ReleaseNotes/21.rst
@@ -60,11 +60,19 @@ Improvements and New Features
 
 - Updated formatting library to Unicode 16.0.0.
 
+- The ``num_put::do_put`` integral overloads have been optimized, resulting in a performance improvement of up to 2.4x.
+
 Deprecations and Removals
 -------------------------
 
 - ``std::is_pod`` and ``std::is_pod_v`` are deprecated in C++20 and later.
 
+Potentially breaking changes
+----------------------------
+
+- The implementation of ``num_put::do_put`` has been replaced to improve the performance, which can lead to different
+  output when printing pointers.
+
 Upcoming Deprecations and Removals
 ----------------------------------
 
diff --git a/libcxx/include/__charconv/tables.h b/libcxx/include/__charconv/tables.h
index 9568bf841cd02..b8c6fd8af0a0f 100644
--- a/libcxx/include/__charconv/tables.h
+++ b/libcxx/include/__charconv/tables.h
@@ -19,16 +19,14 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if _LIBCPP_STD_VER >= 17
-
 namespace __itoa {
 
-inline constexpr char __base_2_lut[64] = {
+inline _LIBCPP_CONSTEXPR const char __base_2_lut[64] = {
     '0', '0', '0', '0', '0', '0', '0', '1', '0', '0', '1', '0', '0', '0', '1', '1', '0', '1', '0', '0', '0', '1',
     '0', '1', '0', '1', '1', '0', '0', '1', '1', '1', '1', '0', '0', '0', '1', '0', '0', '1', '1', '0', '1', '0',
     '1', '0', '1', '1', '1', '1', '0', '0', '1', '1', '0', '1', '1', '1', '1', '0', '1', '1', '1', '1'};
 
-inline constexpr char __base_8_lut[128] = {
+inline _LIBCPP_CONSTEXPR const char __base_8_lut[128] = {
     '0', '0', '0', '1', '0', '2', '0', '3', '0', '4', '0', '5', '0', '6', '0', '7', '1', '0', '1', '1', '1', '2',
     '1', '3', '1', '4', '1', '5', '1', '6', '1', '7', '2', '0', '2', '1', '2', '2', '2', '3', '2', '4', '2', '5',
     '2', '6', '2', '7', '3', '0', '3', '1', '3', '2', '3', '3', '3', '4', '3', '5', '3', '6', '3', '7', '4', '0',
@@ -36,7 +34,7 @@ inline constexpr char __base_8_lut[128] = {
     '5', '4', '5', '5', '5', '6', '5', '7', '6', '0', '6', '1', '6', '2', '6', '3', '6', '4', '6', '5', '6', '6',
     '6', '7', '7', '0', '7', '1', '7', '2', '7', '3', '7', '4', '7', '5', '7', '6', '7', '7'};
 
-inline constexpr char __base_16_lut[512] = {
+inline _LIBCPP_CONSTEXPR const char __base_16_lut[512] = {
     '0', '0', '0', '1', '0', '2', '0', '3', '0', '4', '0', '5', '0', '6', '0', '7', '0', '8', '0', '9', '0', 'a', '0',
     'b', '0', 'c', '0', 'd', '0', 'e', '0', 'f', '1', '0', '1', '1', '1', '2', '1', '3', '1', '4', '1', '5', '1', '6',
     '1', '7', '1', '8', '1', '9', '1', 'a', '1', 'b', '1', 'c', '1', 'd', '1', 'e', '1', 'f', '2', '0', '2', '1', '2',
@@ -61,7 +59,7 @@ inline constexpr char __base_16_lut[512] = {
     '1', 'f', '2', 'f', '3', 'f', '4', 'f', '5', 'f', '6', 'f', '7', 'f', '8', 'f', '9', 'f', 'a', 'f', 'b', 'f', 'c',
     'f', 'd', 'f', 'e', 'f', 'f'};
 
-inline constexpr uint32_t __pow10_32[10] = {
+inline _LIBCPP_CONSTEXPR const uint32_t __pow10_32[10] = {
     UINT32_C(0),
     UINT32_C(10),
     UINT32_C(100),
@@ -73,7 +71,7 @@ inline constexpr uint32_t __pow10_32[10] = {
     UINT32_C(100000000),
     UINT32_C(1000000000)};
 
-inline constexpr uint64_t __pow10_64[20] = {
+inline _LIBCPP_CONSTEXPR const uint64_t __pow10_64[20] = {
     UINT64_C(0),
     UINT64_C(10),
     UINT64_C(100),
@@ -96,8 +94,8 @@ inline constexpr uint64_t __pow10_64[20] = {
     UINT64_C(10000000000000000000)};
 
 #  if _LIBCPP_HAS_INT128
-inline constexpr int __pow10_128_offset      = 0;
-inline constexpr __uint128_t __pow10_128[40] = {
+inline _LIBCPP_CONSTEXPR const int __pow10_128_offset      = 0;
+inline _LIBCPP_CONSTEXPR const __uint128_t __pow10_128[40] = {
     UINT64_C(0),
     UINT64_C(10),
     UINT64_C(100),
@@ -140,7 +138,7 @@ inline constexpr __uint128_t __pow10_128[40] = {
     (__uint128_t(UINT64_C(10000000000000000000)) * UINT64_C(10000000000000000000)) * 10};
 #  endif
 
-inline constexpr char __digits_base_10[200] = {
+inline _LIBCPP_CONSTEXPR const char __digits_base_10[200] = {
     // clang-format off
     '0', '0', '0', '1', '0', '2', '0', '3', '0', '4', '0', '5', '0', '6', '0', '7', '0', '8', '0', '9',
     '1', '0', '1', '1', '1', '2', '1', '3', '1', '4', '1', '5', '1', '6', '1', '7', '1', '8', '1', '9',
@@ -156,8 +154,6 @@ inline constexpr char __digits_base_10[200] = {
 
 } // namespace __itoa
 
-#endif // _LIBCPP_STD_VER >= 17
-
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___CHARCONV_TABLES
diff --git a/libcxx/include/__charconv/to_chars_base_10.h b/libcxx/include/__charconv/to_chars_base_10.h
index 06e4e692337df..d90952ea71f35 100644
--- a/libcxx/include/__charconv/to_chars_base_10.h
+++ b/libcxx/include/__charconv/to_chars_base_10.h
@@ -26,55 +26,53 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if _LIBCPP_STD_VER >= 17
-
 namespace __itoa {
 
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append1(char* __first, uint32_t __value) noexcept {
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append1(char* __first, uint32_t __value) _NOEXCEPT {
   *__first = '0' + static_cast<char>(__value);
   return __first + 1;
 }
 
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append2(char* __first, uint32_t __value) noexcept {
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append2(char* __first, uint32_t __value) _NOEXCEPT {
   return std::copy_n(&__digits_base_10[__value * 2], 2, __first);
 }
 
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append3(char* __first, uint32_t __value) noexcept {
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append3(char* __first, uint32_t __value) _NOEXCEPT {
   return __itoa::__append2(__itoa::__append1(__first, __value / 100), __value % 100);
 }
 
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append4(char* __first, uint32_t __value) noexcept {
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append4(char* __first, uint32_t __value) _NOEXCEPT {
   return __itoa::__append2(__itoa::__append2(__first, __value / 100), __value % 100);
 }
 
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append5(char* __first, uint32_t __value) noexcept {
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append5(char* __first, uint32_t __value) _NOEXCEPT {
   return __itoa::__append4(__itoa::__append1(__first, __value / 10000), __value % 10000);
 }
 
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append6(char* __first, uint32_t __value) noexcept {
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append6(char* __first, uint32_t __value) _NOEXCEPT {
   return __itoa::__append4(__itoa::__append2(__first, __value / 10000), __value % 10000);
 }
 
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append7(char* __first, uint32_t __value) noexcept {
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append7(char* __first, uint32_t __value) _NOEXCEPT {
   return __itoa::__append6(__itoa::__append1(__first, __value / 1000000), __value % 1000000);
 }
 
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append8(char* __first, uint32_t __value) noexcept {
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append8(char* __first, uint32_t __value) _NOEXCEPT {
   return __itoa::__append6(__itoa::__append2(__first, __value / 1000000), __value % 1000000);
 }
 
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append9(char* __first, uint32_t __value) noexcept {
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char* __append9(char* __first, uint32_t __value) _NOEXCEPT {
   return __itoa::__append8(__itoa::__append1(__first, __value / 100000000), __value % 100000000);
 }
 
 template <class _Tp>
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __append10(char* __first, _Tp __value) noexcept {
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __append10(char* __first, _Tp __value) _NOEXCEPT {
   return __itoa::__append8(__itoa::__append2(__first, static_cast<uint32_t>(__value / 100000000)),
                            static_cast<uint32_t>(__value % 100000000));
 }
 
 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char*
-__base_10_u32(char* __first, uint32_t __value) noexcept {
+__base_10_u32(char* __first, uint32_t __value) _NOEXCEPT {
   if (__value < 1000000) {
     if (__value < 10000) {
       if (__value < 100) {
@@ -110,7 +108,7 @@ __base_10_u32(char* __first, uint32_t __value) noexcept {
 }
 
 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char*
-__base_10_u64(char* __buffer, uint64_t __value) noexcept {
+__base_10_u64(char* __buffer, uint64_t __value) _NOEXCEPT {
   if (__value <= UINT32_MAX)
     return __itoa::__base_10_u32(__buffer, static_cast<uint32_t>(__value));
 
@@ -132,13 +130,13 @@ __base_10_u64(char* __buffer, uint64_t __value) noexcept {
 /// \note The lookup table contains a partial set of exponents limiting the
 /// range that can be used. However the range is sufficient for
 /// \ref __base_10_u128.
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline __uint128_t __pow_10(int __exp) noexcept {
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline __uint128_t __pow_10(int __exp) _NOEXCEPT {
   _LIBCPP_ASSERT_INTERNAL(__exp >= __pow10_128_offset, "Index out of bounds");
   return __pow10_128[__exp - __pow10_128_offset];
 }
 
 _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI inline char*
-__base_10_u128(char* __buffer, __uint128_t __value) noexcept {
+__base_10_u128(char* __buffer, __uint128_t __value) _NOEXCEPT {
   _LIBCPP_ASSERT_INTERNAL(
       __value > numeric_limits<uint64_t>::max(), "The optimizations for this algorithm fails when this isn't true.");
 
@@ -179,8 +177,6 @@ __base_10_u128(char* __buffer, __uint128_t __value) noexcept {
 #  endif
 } // namespace __itoa
 
-#endif // _LIBCPP_STD_VER >= 17
-
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
diff --git a/libcxx/include/__charconv/to_chars_integral.h b/libcxx/include/__charconv/to_chars_integral.h
index 710299df9b4da..238c96d7c7a04 100644
--- a/libcxx/include/__charconv/to_chars_integral.h
+++ b/libcxx/include/__charconv/to_chars_integral.h
@@ -39,16 +39,12 @@ _LIBCPP_PUSH_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
+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
+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) {
@@ -60,7 +56,7 @@ __to_chars_itoa(char* __first, char* __last, _Tp __value, true_type) {
 }
 
 template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+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;
@@ -73,7 +69,7 @@ __to_chars_itoa(char* __first, char* __last, _Tp __value, false_type) {
 
 #  if _LIBCPP_HAS_INT128
 template <>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+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.
@@ -92,20 +88,20 @@ __to_chars_itoa(char* __first, char* __last, __uint128_t __value, false_type) {
 }
 #  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 <class _Tp, __enable_if_t<!is_signed<_Tp>::value, int> = 0>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI __to_chars_result
+__to_chars_integral(char* __first, char* __last, _Tp __value, int __base);
 
-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) {
+template <class _Tp, __enable_if_t<is_signed<_Tp>::value, int> = 0>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI __to_chars_result
+__to_chars_integral(char* __first, char* __last, _Tp __value, int __base) {
   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());
+  return std::__to_chars_integral(__first, __last, __x, __base);
 }
 
 namespace __itoa {
@@ -116,7 +112,7 @@ struct _LIBCPP_HIDDEN __integral;
 template <>
 struct _LIBCPP_HIDDEN __integral<2> {
   template <typename _Tp>
-  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
+  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_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.)
@@ -124,7 +120,7 @@ struct _LIBCPP_HIDDEN __integral<2> {
   }
 
   template <typename _Tp>
-  _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result
+  _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);
@@ -152,7 +148,7 @@ struct _LIBCPP_HIDDEN __integral<2> {
 template <>
 struct _LIBCPP_HIDDEN __integral<8> {
   template <typename _Tp>
-  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
+  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_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.)
@@ -160,7 +156,7 @@ struct _LIBCPP_HIDDEN __integral<8> {
   }
 
   template <typename _Tp>
-  _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result
+  _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);
@@ -188,7 +184,7 @@ struct _LIBCPP_HIDDEN __integral<8> {
 template <>
 struct _LIBCPP_HIDDEN __integral<16> {
   template <typename _Tp>
-  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
+  _LIBCPP_HIDE_FROM_ABI static _LIBCPP_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.)
@@ -196,7 +192,7 @@ struct _LIBCPP_HIDDEN __integral<16> {
   }
 
   template <typename _Tp>
-  _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result
+  _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);
@@ -235,13 +231,13 @@ _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __to_chars_integral_widt
 }
 
 template <unsigned _Base, typename _Tp, __enable_if_t<(sizeof(_Tp) >= sizeof(unsigned)), int> = 0>
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+_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, __enable_if_t<(sizeof(_Tp) < sizeof(unsigned)), int> = 0>
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+_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));
 }
@@ -272,9 +268,9 @@ _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __to_chars_integral_widt
   __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) {
+template <class _Tp, __enable_if_t<!is_signed<_Tp>::value, int> >
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI __to_chars_result
+__to_chars_integral(char* __first, char* __last, _Tp __value, int __base) {
   if (__base == 10) [[likely]]
     return std::__to_chars_itoa(__first, __last, __value, false_type());
 
@@ -302,6 +298,28 @@ __to_chars_integral(char* __first, char* __last, _Tp __value, int __base, false_
   return {__last, errc(0)};
 }
 
+_LIBCPP_HIDE_FROM_ABI inline _LIBCPP_CONSTEXPR_SINCE_CXX14 char __hex_to_upper(char __c) {
+  switch (__c) {
+  case 'a':
+    return 'A';
+  case 'b':
+    return 'B';
+  case 'c':
+    return 'C';
+  case 'd':
+    return 'D';
+  case 'e':
+    return 'E';
+  case 'f':
+    return 'F';
+  }
+  return __c;
+}
+
+#if _LIBCPP_STD_VER >= 17
+
+to_chars_result to_chars(char*, char*, bool, int = 10) = delete;
+
 template <typename _Tp, __enable_if_t<is_integral<_Tp>::value, int> = 0>
 inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
 to_chars(char* __first, char* __last, _Tp __value) {
@@ -316,7 +334,7 @@ to_chars(char* __first, char* __last, _Tp __value, int __base) {
   _LIBCPP_ASSERT_UNCATEGORIZED(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>());
+  return std::__to_chars_integral(__first, __last, static_cast<_Type>(__value), __base);
 }
 
 #endif // _LIBCPP_STD_VER >= 17
diff --git a/libcxx/include/__charconv/to_chars_result.h b/libcxx/include/__charconv/to_chars_result.h
index 8df0897a49fbb..41dea4ab14723 100644
--- a/libcxx/include/__charconv/to_chars_result.h
+++ b/libcxx/include/__charconv/to_chars_result.h
@@ -34,6 +34,15 @@ struct _LIBCPP_EXPORTED_FROM_ABI to_chars_result {
 
 #endif // _LIBCPP_STD_VER >= 17
 
+struct __to_chars_result {
+  char* __ptr;
+  errc __ec;
+
+#if _LIBCPP_STD_VER >= 17
+  _LIBCPP_HIDE_FROM_ABI constexpr operator to_chars_result() { return {__ptr, __ec}; }
+#endif
+};
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP___CHARCONV_TO_CHARS_RESULT_H
diff --git a/libcxx/include/__charconv/traits.h b/libcxx/include/__charconv/traits.h
index dd1fa2354436a..085a3f7886f31 100644
--- a/libcxx/include/__charconv/traits.h
+++ b/libcxx/include/__charconv/traits.h
@@ -30,15 +30,13 @@ _LIBCPP_PUSH_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)>> {
+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.
@@ -64,7 +62,7 @@ struct _LIBCPP_HIDDEN __traits_base<_Tp, __enable_if_t<sizeof(_Tp) <= sizeof(uin
 };
 
 template <typename _Tp>
-struct _LIBCPP_HIDDEN __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(uint64_t)>> {
+struct _LIBCPP_HIDDEN __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(uint64_t)> > {
   using type = uint64_t;
 
   /// The width estim...
[truncated]

github-actions · 2025-03-29T08:10:50Z

✅ With the latest revision this PR passed the C/C++ code formatter.

ldionne

Can you add a description of how this is different from the original PR in this PR itself? I looked for differences but it didn't jump at me.

@alexfh Would you be able to take this for a spin internally? To see if you still find some fallout.

ldionne · 2025-04-01T18:27:54Z

More general CC to @llvm/libcxx-vendors since this caused some trouble last time.

philnik777

Can you add a description of how this is different from the original PR in this PR itself? I looked for differences but it didn't jump at me.

Sure. The changes are really subtle.

philnik777 · 2025-04-01T18:31:34Z

libcxx/include/locale

+
+  // Maybe add '+' prefix
+  if (std::is_signed<_Integral>::value && (__flags & ios_base::showpos) && __basefield != ios_base::oct &&
+      __basefield != ios_base::hex && __v >= 0)


This >= was a > before.

philnik777 · 2025-04-01T18:31:49Z

libcxx/include/locale

+    *__buffer_ptr++ = '+';
+
+    // Add base prefix
+  if (__v != 0 && __flags & ios_base::showbase) {


The __v != 0 wasn't there before.

ldionne

LGTM, please update the commit message.

Please give 48h for @alexfh to reply in case they want to take this for a spin internally.

nico · 2025-04-09T14:35:53Z

Can you add a description of how this is different from the original PR in this PR itself? I looked for differences but it didn't jump at me.

(Aside: One way to handle relands is to have a pure reland commit that just reverts the revert without any changes as first commit on the PR, and then a second commit on the PR that has the fixups. That makes it easy to see what changed. Maybe that's something y'all want to adopt for relands.)

This reverts commit d1156fc.

nico · 2025-04-13T21:56:40Z

libcxx/docs/ReleaseNotes/21.rst

+----------------------------
+
+- The implementation of ``num_put::do_put`` has been replaced to improve the performance, which can lead to different
+  output when printing pointers.


It always leads to different output on Windows, right? libc++ never printed a 0x prefix on pointers on Windows before, and now it always does (making it consistent with libc++ on other platforms, and inconsistent with Microsoft's STL as far as I know). Maybe the release notes could be more precise about this :)

…lvm#133572) This reverts commit d1156fc. This patch fixes the reported incorrect formatting changes and adds tests for them. The performance should be unaffected, since there are no significant changes required to fix the bugs. Specifically, a `>` was changed to a `>=` to also add a `+` in the zero case, and we're checking for zero now before printing the octal and hexadecimal prefixes. Closes llvm#131710

asmok-g · 2025-04-22T14:37:08Z

As for google internal testing, what we see is a bunch of golden-tests failing due to the change in nullptr formatting from (nil) to 0.

After 8fc2538 "Reapply '[libc++] Optimize num_put integral functions' (#131613) (#133572)", including <locale> in C++03 mode with Debug hardening enabled fails. This patch fixes that by applying a workaround used elsewhere to construct errc in C++03 mode.

philnik777 requested a review from a team as a code owner March 29, 2025 08:08

llvmbot added the libc++ libc++ C++ Standard Library. Not GNU libstdc++. Not libc++abi. label Mar 29, 2025

ldionne reviewed Apr 1, 2025

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philnik777 commented Apr 1, 2025

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ldionne approved these changes Apr 2, 2025

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ldionne added the performance label Apr 2, 2025

ldionne assigned philnik777 Apr 2, 2025

Reapply "[libc++] Optimize num_put integral functions" (llvm#131613)

ad6cbd6

This reverts commit d1156fc.

philnik777 force-pushed the optimize_num_put branch from 0df8080 to ad6cbd6 Compare April 11, 2025 13:33

philnik777 merged commit 8fc2538 into llvm:main Apr 11, 2025
14 of 21 checks passed

philnik777 deleted the optimize_num_put branch April 11, 2025 13:36

nico reviewed Apr 13, 2025

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stbergmann mentioned this pull request May 5, 2025

Fix use of std::errc() for C++ < 11 #138522

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