[libc++][chrono] P2592R3: Hashing for chrono #165132

rsaddatimov · 2025-10-26T05:34:28Z

github-actions · 2025-10-26T05:34:50Z

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llvmbot · 2025-10-26T05:35:41Z

@llvm/pr-subscribers-libcxx

Author: Rafail Shakhin ogly (rsaddatimov)

Changes

Patch is 20.57 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/165132.diff

18 Files Affected:

(modified) libcxx/docs/FeatureTestMacroTable.rst (+1-1)
(modified) libcxx/docs/ReleaseNotes/22.rst (+1)
(modified) libcxx/docs/Status/Cxx2cPapers.csv (+1-1)
(modified) libcxx/include/__chrono/day.h (+8)
(modified) libcxx/include/__chrono/duration.h (+13)
(modified) libcxx/include/__chrono/leap_second.h (+8)
(modified) libcxx/include/__chrono/month.h (+8)
(modified) libcxx/include/__chrono/month_weekday.h (+15)
(modified) libcxx/include/__chrono/monthday.h (+15)
(modified) libcxx/include/__chrono/time_point.h (+14)
(modified) libcxx/include/__chrono/weekday.h (+22)
(modified) libcxx/include/__chrono/year.h (+8)
(modified) libcxx/include/__chrono/year_month.h (+8)
(modified) libcxx/include/__chrono/year_month_day.h (+15)
(modified) libcxx/include/__chrono/year_month_weekday.h (+17)
(modified) libcxx/include/__chrono/zoned_time.h (+10)
(modified) libcxx/include/version (+2-2)
(added) libcxx/test/std/time/time.hash/time.hash_enabled.pass.cpp (+55)

diff --git a/libcxx/docs/FeatureTestMacroTable.rst b/libcxx/docs/FeatureTestMacroTable.rst
index 8fba6db871f08..a878c46d35cbe 100644
--- a/libcxx/docs/FeatureTestMacroTable.rst
+++ b/libcxx/docs/FeatureTestMacroTable.rst
@@ -88,7 +88,7 @@ Status
     ---------------------------------------------------------- -----------------
     ``__cpp_lib_byte``                                         ``201603L``
     ---------------------------------------------------------- -----------------
-    ``__cpp_lib_chrono``                                       ``201611L``
+    ``__cpp_lib_chrono``                                       ``202510L``
     ---------------------------------------------------------- -----------------
     ``__cpp_lib_clamp``                                        ``201603L``
     ---------------------------------------------------------- -----------------
diff --git a/libcxx/docs/ReleaseNotes/22.rst b/libcxx/docs/ReleaseNotes/22.rst
index 25d33a9c2eb50..7ea3529642c90 100644
--- a/libcxx/docs/ReleaseNotes/22.rst
+++ b/libcxx/docs/ReleaseNotes/22.rst
@@ -38,6 +38,7 @@ What's New in Libc++ 22.0.0?
 Implemented Papers
 ------------------
 
+- P2592R3: Hashing support for ``std::chrono`` value classes (`Github <https://llvm.org/PR105358>`__)
 - P2321R2: ``zip`` (`Github <https://llvm.org/PR105169>`__) (The paper is partially implemented. ``zip_transform_view``
   is implemented in this release)
 - P3044R2: sub-``string_view`` from ``string`` (`Github <https://llvm.org/PR148140>`__)
diff --git a/libcxx/docs/Status/Cxx2cPapers.csv b/libcxx/docs/Status/Cxx2cPapers.csv
index a5423acf0d419..493e6a3c9ed44 100644
--- a/libcxx/docs/Status/Cxx2cPapers.csv
+++ b/libcxx/docs/Status/Cxx2cPapers.csv
@@ -1,6 +1,6 @@
 "Paper #","Paper Name","Meeting","Status","First released version","GitHub issue","Notes"
 "`P2497R0 <https://wg21.link/P2497R0>`__","Testing for success or failure of ``<charconv>`` functions","2023-06 (Varna)","|Complete|","18","`#105357 <https://github.com/llvm/llvm-project/issues/105357>`__",""
-"`P2592R3 <https://wg21.link/P2592R3>`__","Hashing support for ``std::chrono`` value classes","2023-06 (Varna)","","","`#105358 <https://github.com/llvm/llvm-project/issues/105358>`__",""
+"`P2592R3 <https://wg21.link/P2592R3>`__","Hashing support for ``std::chrono`` value classes","2023-06 (Varna)","|Complete|","22","`#105358 <https://github.com/llvm/llvm-project/issues/105358>`__",""
 "`P2587R3 <https://wg21.link/P2587R3>`__","``to_string`` or not ``to_string``","2023-06 (Varna)","","","`#105359 <https://github.com/llvm/llvm-project/issues/105359>`__",""
 "`P2562R1 <https://wg21.link/P2562R1>`__","``constexpr`` Stable Sorting","2023-06 (Varna)","|Complete|","21","`#105360 <https://github.com/llvm/llvm-project/issues/105360>`__",""
 "`P2545R4 <https://wg21.link/P2545R4>`__","Read-Copy Update (RCU)","2023-06 (Varna)","","","`#105361 <https://github.com/llvm/llvm-project/issues/105361>`__",""
diff --git a/libcxx/include/__chrono/day.h b/libcxx/include/__chrono/day.h
index f5b14689a78ac..5c39bf16f72ea 100644
--- a/libcxx/include/__chrono/day.h
+++ b/libcxx/include/__chrono/day.h
@@ -13,6 +13,7 @@
 #include <__chrono/duration.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -92,6 +93,13 @@ _LIBCPP_HIDE_FROM_ABI inline constexpr day& day::operator-=(const days& __dd) no
 
 } // namespace chrono
 
+template <>
+struct hash<chrono::day> : public __unary_function<chrono::day, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::day& __d) const _NOEXCEPT {
+    return hash<unsigned>{}(static_cast<unsigned>(__d));
+  }
+};
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20
diff --git a/libcxx/include/__chrono/duration.h b/libcxx/include/__chrono/duration.h
index 57fa64d650068..3e04891f5b0c6 100644
--- a/libcxx/include/__chrono/duration.h
+++ b/libcxx/include/__chrono/duration.h
@@ -13,6 +13,7 @@
 #include <__compare/ordering.h>
 #include <__compare/three_way_comparable.h>
 #include <__config>
+#include <__functional/hash.h>
 #include <__type_traits/common_type.h>
 #include <__type_traits/enable_if.h>
 #include <__type_traits/is_convertible.h>
@@ -538,6 +539,18 @@ using namespace literals::chrono_literals;
 
 #endif // _LIBCPP_STD_VER >= 14
 
+#if _LIBCPP_STD_VER >= 20
+
+template <class _Rep, class _Period>
+  requires __has_enabled_hash<_Rep>::value
+struct hash<chrono::duration<_Rep, _Period>> : public __unary_function<chrono::duration<_Rep, _Period>, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::duration<_Rep, _Period>& __d) const {
+    return hash<_Rep>{}(__d.count());
+  }
+};
+
+#endif // _LIBCPP_STD_VER >= 20
+
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
diff --git a/libcxx/include/__chrono/leap_second.h b/libcxx/include/__chrono/leap_second.h
index 1857bef80376e..cf7a2c16626d0 100644
--- a/libcxx/include/__chrono/leap_second.h
+++ b/libcxx/include/__chrono/leap_second.h
@@ -22,6 +22,7 @@
 #  include <__compare/ordering.h>
 #  include <__compare/three_way_comparable.h>
 #  include <__config>
+#  include <__functional/hash.h>
 #  include <__utility/private_constructor_tag.h>
 
 #  if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -122,6 +123,13 @@ class leap_second {
 
 } // namespace chrono
 
+template <>
+struct hash<chrono::leap_second> : public __unary_function<chrono::leap_second, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::leap_second& __lp) const _NOEXCEPT {
+    return hash<chrono::seconds>{}(__lp.value());
+  }
+};
+
 #  endif // _LIBCPP_STD_VER >= 20
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/libcxx/include/__chrono/month.h b/libcxx/include/__chrono/month.h
index 77c67d0954efa..d76efd4973193 100644
--- a/libcxx/include/__chrono/month.h
+++ b/libcxx/include/__chrono/month.h
@@ -13,6 +13,7 @@
 #include <__chrono/duration.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -108,6 +109,13 @@ inline constexpr month December{12};
 
 } // namespace chrono
 
+template <>
+struct hash<chrono::month> : public __unary_function<chrono::month, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::month& __m) const _NOEXCEPT {
+    return hash<unsigned>{}(static_cast<unsigned>(__m));
+  }
+};
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20
diff --git a/libcxx/include/__chrono/month_weekday.h b/libcxx/include/__chrono/month_weekday.h
index 7919879655214..a46526eca2853 100644
--- a/libcxx/include/__chrono/month_weekday.h
+++ b/libcxx/include/__chrono/month_weekday.h
@@ -13,6 +13,7 @@
 #include <__chrono/month.h>
 #include <__chrono/weekday.h>
 #include <__config>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -98,6 +99,20 @@ _LIBCPP_HIDE_FROM_ABI inline constexpr month_weekday_last operator/(const weekda
 }
 } // namespace chrono
 
+template <>
+struct hash<chrono::month_weekday> : public __unary_function<chrono::month_weekday, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::month_weekday& __mw) const _NOEXCEPT {
+    return hash<chrono::month>{}(__mw.month()) ^ hash<chrono::weekday_indexed>{}(__mw.weekday_indexed());
+  }
+};
+
+template <>
+struct hash<chrono::month_weekday_last> : public __unary_function<chrono::month_weekday_last, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::month_weekday_last& __mwl) const _NOEXCEPT {
+    return hash<chrono::month>{}(__mwl.month()) ^ hash<chrono::weekday_last>{}(__mwl.weekday_last());
+  }
+};
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20
diff --git a/libcxx/include/__chrono/monthday.h b/libcxx/include/__chrono/monthday.h
index 57712cf0b65a8..79c2a4c9f0a42 100644
--- a/libcxx/include/__chrono/monthday.h
+++ b/libcxx/include/__chrono/monthday.h
@@ -15,6 +15,7 @@
 #include <__chrono/month.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -126,6 +127,20 @@ _LIBCPP_HIDE_FROM_ABI inline constexpr month_day_last operator/(last_spec, int _
 
 } // namespace chrono
 
+template <>
+struct hash<chrono::month_day> : public __unary_function<chrono::month_day, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::month_day& __md) const _NOEXCEPT {
+    return hash<chrono::month>{}(__md.month()) ^ hash<chrono::day>{}(__md.day());
+  }
+};
+
+template <>
+struct hash<chrono::month_day_last> : public __unary_function<chrono::month_day_last, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::month_day_last& __mdl) const _NOEXCEPT {
+    return hash<chrono::month>{}(__mdl.month());
+  }
+};
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20
diff --git a/libcxx/include/__chrono/time_point.h b/libcxx/include/__chrono/time_point.h
index bc2c7798a630b..02720ec66228e 100644
--- a/libcxx/include/__chrono/time_point.h
+++ b/libcxx/include/__chrono/time_point.h
@@ -14,6 +14,7 @@
 #include <__compare/ordering.h>
 #include <__compare/three_way_comparable.h>
 #include <__config>
+#include <__functional/hash.h>
 #include <__type_traits/common_type.h>
 #include <__type_traits/enable_if.h>
 #include <__type_traits/is_convertible.h>
@@ -224,6 +225,19 @@ operator-(const time_point<_Clock, _Duration1>& __lhs, const time_point<_Clock,
 
 } // namespace chrono
 
+#if _LIBCPP_STD_VER >= 20
+
+template <class _Clock, class _Duration>
+  requires __has_enabled_hash<_Duration>::value
+struct hash<chrono::time_point<_Clock, _Duration>>
+    : public __unary_function<chrono::time_point<_Clock, _Duration>, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::time_point<_Clock, _Duration>& __tp) const {
+    return hash<_Duration>{}(__tp.time_since_epoch());
+  }
+};
+
+#endif // _LIBCPP_STD_VER >= 20
+
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
diff --git a/libcxx/include/__chrono/weekday.h b/libcxx/include/__chrono/weekday.h
index 728cbb844633f..2fc988a9f4b57 100644
--- a/libcxx/include/__chrono/weekday.h
+++ b/libcxx/include/__chrono/weekday.h
@@ -15,6 +15,7 @@
 #include <__chrono/system_clock.h>
 #include <__chrono/time_point.h>
 #include <__config>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -160,6 +161,27 @@ inline constexpr weekday Saturday{6};
 
 } // namespace chrono
 
+template <>
+struct hash<chrono::weekday> : public __unary_function<chrono::weekday, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::weekday& __w) const _NOEXCEPT {
+    return hash<unsigned>{}(__w.c_encoding());
+  }
+};
+
+template <>
+struct hash<chrono::weekday_indexed> : public __unary_function<chrono::weekday_indexed, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::weekday_indexed& __wi) const _NOEXCEPT {
+    return hash<chrono::weekday>{}(__wi.weekday()) ^ hash<unsigned>{}(__wi.index());
+  }
+};
+
+template <>
+struct hash<chrono::weekday_last> : public __unary_function<chrono::weekday_last, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::weekday_last& __wl) const _NOEXCEPT {
+    return hash<chrono::weekday>{}(__wl.weekday());
+  }
+};
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20
diff --git a/libcxx/include/__chrono/year.h b/libcxx/include/__chrono/year.h
index 2ae5180cb8fc9..4ee4186dcf533 100644
--- a/libcxx/include/__chrono/year.h
+++ b/libcxx/include/__chrono/year.h
@@ -13,6 +13,7 @@
 #include <__chrono/duration.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__functional/hash.h>
 #include <limits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -109,6 +110,13 @@ _LIBCPP_HIDE_FROM_ABI constexpr bool year::ok() const noexcept {
 
 } // namespace chrono
 
+template <>
+struct hash<chrono::year> : public __unary_function<chrono::year, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::year& __y) const _NOEXCEPT {
+    return hash<int>{}(static_cast<int>(__y));
+  }
+};
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20
diff --git a/libcxx/include/__chrono/year_month.h b/libcxx/include/__chrono/year_month.h
index cf9234bdb4625..a3e1429527bea 100644
--- a/libcxx/include/__chrono/year_month.h
+++ b/libcxx/include/__chrono/year_month.h
@@ -15,6 +15,7 @@
 #include <__chrono/year.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -116,6 +117,13 @@ _LIBCPP_HIDE_FROM_ABI inline constexpr year_month& year_month::operator-=(const
 
 } // namespace chrono
 
+template <>
+struct hash<chrono::year_month> : public __unary_function<chrono::year_month, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::year_month& __ym) const _NOEXCEPT {
+    return hash<chrono::year>{}(__ym.year()) ^ hash<chrono::month>{}(__ym.month());
+  }
+};
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20
diff --git a/libcxx/include/__chrono/year_month_day.h b/libcxx/include/__chrono/year_month_day.h
index a0510a14f4ede..b0c05716bdba3 100644
--- a/libcxx/include/__chrono/year_month_day.h
+++ b/libcxx/include/__chrono/year_month_day.h
@@ -21,6 +21,7 @@
 #include <__chrono/year_month.h>
 #include <__compare/ordering.h>
 #include <__config>
+#include <__functional/hash.h>
 #include <limits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -330,6 +331,20 @@ _LIBCPP_HIDE_FROM_ABI inline constexpr bool year_month_day::ok() const noexcept
 
 } // namespace chrono
 
+template <>
+struct hash<chrono::year_month_day> : public __unary_function<chrono::year_month_day, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::year_month_day& __ymd) const _NOEXCEPT {
+    return hash<chrono::year>{}(__ymd.year()) ^ hash<chrono::month>{}(__ymd.month()) ^ hash<chrono::day>{}(__ymd.day());
+  }
+};
+
+template <>
+struct hash<chrono::year_month_day_last> : public __unary_function<chrono::year_month_day_last, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::year_month_day_last& __ymdl) const _NOEXCEPT {
+    return hash<chrono::year>{}(__ymdl.year()) ^ hash<chrono::month_day_last>{}(__ymdl.month_day_last());
+  }
+};
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20
diff --git a/libcxx/include/__chrono/year_month_weekday.h b/libcxx/include/__chrono/year_month_weekday.h
index 0c3dd494c8787..6ae704c397b97 100644
--- a/libcxx/include/__chrono/year_month_weekday.h
+++ b/libcxx/include/__chrono/year_month_weekday.h
@@ -22,6 +22,7 @@
 #include <__chrono/year_month.h>
 #include <__chrono/year_month_day.h>
 #include <__config>
+#include <__functional/hash.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
@@ -280,6 +281,22 @@ year_month_weekday_last::operator-=(const years& __dy) noexcept {
 
 } // namespace chrono
 
+template <>
+struct hash<chrono::year_month_weekday> : public __unary_function<chrono::year_month_weekday, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::year_month_weekday& __ymw) const _NOEXCEPT {
+    return hash<chrono::year>{}(__ymw.year()) ^ hash<chrono::month>{}(__ymw.month()) ^
+           hash<chrono::weekday_indexed>{}(__ymw.weekday_indexed());
+  }
+};
+
+template <>
+struct hash<chrono::year_month_weekday_last> : public __unary_function<chrono::year_month_weekday_last, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::year_month_weekday_last& __ymwl) const _NOEXCEPT {
+    return hash<chrono::year>{}(__ymwl.year()) ^ hash<chrono::month>{}(__ymwl.month()) ^
+           hash<chrono::weekday_last>{}(__ymwl.weekday_last());
+  }
+};
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER >= 20
diff --git a/libcxx/include/__chrono/zoned_time.h b/libcxx/include/__chrono/zoned_time.h
index 8db687a422ab1..5f110d1721502 100644
--- a/libcxx/include/__chrono/zoned_time.h
+++ b/libcxx/include/__chrono/zoned_time.h
@@ -24,6 +24,7 @@
 #  include <__chrono/tzdb_list.h>
 #  include <__concepts/constructible.h>
 #  include <__config>
+#  include <__functional/hash.h>
 #  include <__type_traits/common_type.h>
 #  include <__type_traits/conditional.h>
 #  include <__type_traits/remove_cvref.h>
@@ -216,6 +217,15 @@ operator==(const zoned_time<_Duration1, _TimeZonePtr>& __lhs, const zoned_time<_
 
 } // namespace chrono
 
+template <class _Duration, class _TimeZonePtr>
+  requires __has_enabled_hash<_Duration>::value && __has_enabled_hash<_TimeZonePtr>::value
+struct hash<chrono::zoned_time<_Duration, _TimeZonePtr>>
+    : public __unary_function<chrono::zoned_time<_Duration, _TimeZonePtr>, size_t> {
+  _LIBCPP_HIDE_FROM_ABI size_t operator()(const chrono::zoned_time<_Duration, _TimeZonePtr>& __zt) const {
+    return hash<chrono::sys_time<_Duration>>{}(__zt.get_sys_time()) ^ hash<_TimeZonePtr>{}(__zt.get_time_zone());
+  }
+};
+
 #  endif // _LIBCPP_STD_VER >= 20 && _LIBCPP_HAS_TIME_ZONE_DATABASE && _LIBCPP_HAS_FILESYSTEM &&
          // _LIBCPP_HAS_LOCALIZATION
 
diff --git a/libcxx/include/version b/libcxx/include/version
index 0fef1bb87cf60..5200d72ed1ea5 100644
--- a/libcxx/include/version
+++ b/libcxx/include/version
@@ -57,7 +57,7 @@ __cpp_lib_byteswap                                      202110L <bit>
 __cpp_lib_char8_t                                       201907L <atomic> <filesystem> <istream>
                                                                 <limits> <locale> <ostream>
                                                                 <string> <string_view>
-__cpp_lib_chrono                                        201611L <chrono>
+__cpp_lib_chrono                                        202510L <chrono>
 __cpp_lib_chrono_udls                                   201304L <chrono>
 __cpp_lib_clamp                                         201603L <algorithm>
 __cpp_lib_common_reference                              202302L <type_traits>
@@ -332,7 +332,7 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # define __cpp_lib_bool_constant                        201505L
 # define __cpp_lib_boyer_moore_searcher                 201603L
 # define __cpp_lib_byte                                 201603L
-# define __cpp_lib_chrono                               201611L
+# define __cpp_lib_chrono                               202510L
 # define __cpp_lib_clamp                                201603L
 # define __cpp_lib_enable_shared_from_this              201603L
 // # define __cpp_lib_execution                            201603L
diff --git a/libcxx/test/std/time/time.hash/time.hash_enabled.pass.cpp b/libcxx/test/std/time/time.hash/time.hash_enabled.pass.cpp
new file mode 100644
index 0000000000000..e935a121c0ab0
--- /dev/null
+++ b/libcxx/test/std/time/time.hash/time.hash_enabled.pass.cpp
@@ -0,0 +1,55 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17
+
+// <chrono>
+
+// Test that <chrono> provides all of the hash specializations.
+
+#include <chrono>
+#include "poisoned_hash_helper.h"
+namespace chrono = std::chrono;
+
+int main(int, char**) {
+  test_hash_enabled<chrono::nanoseconds>();
+  test_hash_enabled<chrono::microseconds>();
+  test_hash_enabled<chrono::milliseconds>();
+  test_hash_enabled<chrono::seconds>();
+  test_hash_enabled<chrono::minutes>();
+  test_hash_enabled<chrono::hours>();
+  test_hash_enabled<chrono::days>();
+  test_hash_enabled<chrono::weeks>();
+  test_hash_enabled<chrono::months>();
+  test_hash_enabled<chrono::years>();
+
+  test_hash_enabled<chrono::day>();
+  test_hash_enabled<chrono::month>();
+  test_hash_enabled<chrono::year>();
+
+  test_hash_enabled<chrono::weekday>();
+  test_hash_enabled<chrono::weekday_indexed>();
+  test_hash_enabled(chrono::weekday_last(chrono::weekday{}));
+
+  test_hash_enabled<chrono::month_day>();
+  test_hash_enabled(chrono::month_day_last(chrono::month{}));
+
+  test_hash_enabled(chro...
[truncated]

H-G-Hristov · 2025-10-26T06:17:41Z

@rsaddatimov Thank you for working on this. You need to add a description to the top comment which is the commit message. We track the implementation status via GitHub issues. The very least you need to do is to add "Closes P2592R3: Hashing support for std::chrono value classes #105358", according to the GitHub syntax to associate this PR with the issue.

P.S. I updated the description accordingly.

I't looks like you did not update the version value correctly. You need to run the script to update the value. An example [libc++][atomic] P2835R7: Expose std::atomic_ref's object address #162236
You might need to have to update the synopsis too.

libcxx/test/std/time/time.hash/time.hash_enabled.pass.cpp

libcxx/include/__chrono/duration.h

libcxx/test/std/time/time.hash/time.hash_enabled.pass.cpp

libcxx/include/__chrono/day.h

libcxx/include/__chrono/month_weekday.h

libcxx/utils/generate_feature_test_macro_components.py

frederick-vs-ja · 2025-10-27T08:52:10Z

libcxx/include/__chrono/day.h

+
+template <>
+struct hash<chrono::day> {
+  _LIBCPP_HIDE_FROM_ABI static size_t operator()(const chrono::day& __d) noexcept {


Test failures indicated that we should include <__cstddef/size_t.h> in every header where hash specialization is being added.

frederick-vs-ja · 2025-10-27T09:04:19Z

libcxx/include/__chrono/duration.h

 #include <__compare/ordering.h>
 #include <__compare/three_way_comparable.h>
 #include <__config>
+#include <__functional/hash.h>


I thing we can ~~either~~

add <__chrono/duration_hash.h> and <__chrono/time_point_hash.h> (together with changes to CMakeList.txt and module.modulemap.in) and move hash specializations into them, which avoids changing transitive includes; or

just modify libcxx/test/libcxx/transitive_includes/cxx26.csv to add entries memory_resource cstring, mutex cstring, and shared_mutex cstring to resolve test failures about transitive includes.

~~I'm not sure which approach is better. The first one is more complicated but possibly better for compiler throughput.~~

Perhaps we should go for the second approach. The first one is likely to raise ODR violation.

Initial hashing support for chrono

1c6dc8d

rsaddatimov requested a review from a team as a code owner October 26, 2025 05:34

llvmbot added the libc++ libc++ C++ Standard Library. Not GNU libstdc++. Not libc++abi. label Oct 26, 2025

H-G-Hristov reviewed Oct 26, 2025

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H-G-Hristov reviewed Oct 26, 2025

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H-G-Hristov reviewed Oct 26, 2025

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rsaddatimov added 3 commits October 26, 2025 17:51

Update version via script

0546b76

Wrap around c++26 macro and test fix

15fa9ec

Add synopsis

ca5a16f

frederick-vs-ja requested changes Oct 27, 2025

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Fix issues & revert version bump

f39e93b

rsaddatimov force-pushed the P2592R3-chrono-hash branch from e748d78 to f39e93b Compare October 27, 2025 05:48

frederick-vs-ja reviewed Oct 27, 2025

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frederick-vs-ja requested review from ldionne and philnik777 October 27, 2025 09:04

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[libc++][chrono] P2592R3: Hashing for chrono #165132

[libc++][chrono] P2592R3: Hashing for chrono #165132

rsaddatimov commented Oct 26, 2025 •

edited by Zingam

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