[libcxx-commits] [libcxx] [libcxx] Implement C++20 std::chrono::is_clock, std::chrono::is_clock_v (PR #160607)
Yuxuan Chen via libcxx-commits
libcxx-commits at lists.llvm.org
Tue Sep 30 10:44:04 PDT 2025
https://github.com/yuxuanchen1997 updated https://github.com/llvm/llvm-project/pull/160607
>From 74f494a9bc8920202b31681db2ce1e61fa446730 Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at meta.com>
Date: Wed, 24 Sep 2025 11:54:36 -0700
Subject: [PATCH 01/13] [libcxx] Implement C++20 std::chrono::is_clock,
std::chrono::is_clock_v
---
libcxx/docs/ReleaseNotes/22.rst | 2 +
libcxx/include/CMakeLists.txt | 1 +
libcxx/include/__chrono/is_clock.h | 49 +++++++
libcxx/include/chrono | 1 +
libcxx/include/module.modulemap.in | 4 +
libcxx/modules/std/chrono.inc | 4 +-
.../trait.is.clock.pass.cpp | 129 ++++++++++++++++++
7 files changed, 188 insertions(+), 2 deletions(-)
create mode 100644 libcxx/include/__chrono/is_clock.h
create mode 100644 libcxx/test/std/time/time.traits.is.clock/trait.is.clock.pass.cpp
diff --git a/libcxx/docs/ReleaseNotes/22.rst b/libcxx/docs/ReleaseNotes/22.rst
index 509ead64ee525..b4261e474a27b 100644
--- a/libcxx/docs/ReleaseNotes/22.rst
+++ b/libcxx/docs/ReleaseNotes/22.rst
@@ -41,6 +41,8 @@ Implemented Papers
- P2321R2: ``zip`` (`Github <https://llvm.org/PR105169>`__) (The paper is partially implemented. ``zip_transform_view``
is implemented in this release)
- P3168R2: Give ``std::optional`` Range Support (`Github <https://llvm.org/PR105430>`__)
+- P0355R7: ``std::chrono::is_clock`` and ``std::chrono::is_clock_v`` (`Github <https://llvm.org/PR160607>` __)
+ (The paper is partially implemented. ``is_clock`` and ``is_clock_v`` is implemented in this release)
Improvements and New Features
-----------------------------
diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index e050362abb658..cb52105ab0ebd 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -262,6 +262,7 @@ set(files
__chrono/gps_clock.h
__chrono/hh_mm_ss.h
__chrono/high_resolution_clock.h
+ __chrono/is_clock.h
__chrono/leap_second.h
__chrono/literals.h
__chrono/local_info.h
diff --git a/libcxx/include/__chrono/is_clock.h b/libcxx/include/__chrono/is_clock.h
new file mode 100644
index 0000000000000..877d31ad31176
--- /dev/null
+++ b/libcxx/include/__chrono/is_clock.h
@@ -0,0 +1,49 @@
+// -*- 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___CHRONO_IS_CLOCK_H
+#define _LIBCPP___CHRONO_IS_CLOCK_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+# pragma GCC system_header
+#endif
+
+#if _LIBCPP_STD_VER >= 20
+
+# include <__type_traits/integral_constant.h>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace chrono {
+
+template <class>
+struct is_clock : std::false_type {};
+
+template <class _Tp>
+ requires requires {
+ typename _Tp::rep;
+ typename _Tp::period;
+ typename _Tp::duration;
+ typename _Tp::time_point;
+ _Tp::is_steady;
+ _Tp::now();
+ }
+struct is_clock<_Tp> : std::true_type {};
+
+template <class _Tp>
+_LIBCPP_NO_SPECIALIZATIONS inline constexpr bool is_clock_v = is_clock<_Tp>::value;
+
+} // namespace chrono
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_STD_VER
+#endif // _LIBCPP___CHRONO_IS_CLOCK_H
diff --git a/libcxx/include/chrono b/libcxx/include/chrono
index 82e99a31bcc9f..f3bb08ef386c9 100644
--- a/libcxx/include/chrono
+++ b/libcxx/include/chrono
@@ -1057,6 +1057,7 @@ constexpr chrono::year operator ""y(unsigned lo
# include <__chrono/day.h>
# include <__chrono/exception.h>
# include <__chrono/hh_mm_ss.h>
+# include <__chrono/is_clock.h>
# include <__chrono/literals.h>
# include <__chrono/local_info.h>
# include <__chrono/month.h>
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index dc1933324ef79..e94384cbe338b 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -970,6 +970,10 @@ module std [system] {
header "__chrono/high_resolution_clock.h"
export *
}
+ module is_clock {
+ header "__chrono/is_clock.h"
+ export std_core.type_traits.integral_constant
+ }
module leap_second {
header "__chrono/leap_second.h"
}
diff --git a/libcxx/modules/std/chrono.inc b/libcxx/modules/std/chrono.inc
index 66eccd8d290ad..db405d482bf9e 100644
--- a/libcxx/modules/std/chrono.inc
+++ b/libcxx/modules/std/chrono.inc
@@ -25,8 +25,8 @@ export namespace std {
using std::chrono::duration_values;
- // using std::chrono::is_clock;
- // using std::chrono::is_clock_v;
+ using std::chrono::is_clock;
+ using std::chrono::is_clock_v;
// [time.duration.nonmember], duration arithmetic
using std::chrono::operator+;
diff --git a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.pass.cpp b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.pass.cpp
new file mode 100644
index 0000000000000..1abdf255054b3
--- /dev/null
+++ b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.pass.cpp
@@ -0,0 +1,129 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: std-at-least-c++20
+
+#include <chrono>
+#include <ratio>
+
+struct EmptyStruct {};
+
+// Test structs missing required members
+struct MissingRep {
+ using period = std::ratio<1>;
+ using duration = std::chrono::seconds;
+ using time_point = std::chrono::time_point<MissingRep>;
+ static constexpr bool is_steady = false;
+ static time_point now();
+};
+
+struct MissingPeriod {
+ using rep = long;
+ using duration = std::chrono::seconds;
+ using time_point = std::chrono::time_point<MissingPeriod>;
+ static constexpr bool is_steady = false;
+ static time_point now();
+};
+
+struct MissingDuration {
+ using rep = long;
+ using time_point = long;
+ static constexpr bool is_steady = false;
+ static time_point now();
+};
+
+struct MissingTimePoint {
+ using rep = long;
+ using period = std::ratio<1>;
+ using duration = std::chrono::seconds;
+ static constexpr bool is_steady = false;
+ static std::chrono::time_point<MissingTimePoint> now();
+};
+
+struct MissingIsSteady {
+ using rep = long;
+ using period = std::ratio<1>;
+ using duration = std::chrono::seconds;
+ using time_point = std::chrono::time_point<MissingIsSteady>;
+ static time_point now();
+};
+
+struct MissingNow {
+ using rep = long;
+ using period = std::ratio<1>;
+ using duration = std::chrono::seconds;
+ using time_point = std::chrono::time_point<MissingNow>;
+ static constexpr bool is_steady = false;
+};
+
+// Valid clock types
+struct ValidSteadyClock {
+ using rep = long long;
+ using period = std::nano;
+ using duration = std::chrono::nanoseconds;
+ using time_point = std::chrono::time_point<ValidSteadyClock>;
+ static constexpr bool is_steady = true;
+ static time_point now();
+};
+
+struct ValidSystemClock {
+ using rep = int64_t;
+ using period = std::micro;
+ using duration = std::chrono::microseconds;
+ using time_point = std::chrono::time_point<ValidSystemClock>;
+ static constexpr bool is_steady = false;
+ static time_point now();
+};
+
+int main(int, char**) {
+ // Test both is_clock and is_clock_v
+ static_assert(std::chrono::is_clock<std::chrono::system_clock>::value);
+ static_assert(std::chrono::is_clock_v<std::chrono::system_clock>);
+
+ // Test standard clock types
+ static_assert(std::chrono::is_clock_v<std::chrono::system_clock>);
+ static_assert(std::chrono::is_clock_v<std::chrono::steady_clock>);
+ static_assert(std::chrono::is_clock_v<std::chrono::high_resolution_clock>);
+
+ // Test non-clock types
+ static_assert(!std::chrono::is_clock_v<EmptyStruct>);
+ static_assert(!std::chrono::is_clock_v<int>);
+ static_assert(!std::chrono::is_clock_v<void>);
+ static_assert(!std::chrono::is_clock_v<std::chrono::system_clock::time_point>);
+ static_assert(!std::chrono::is_clock_v<std::chrono::steady_clock::time_point>);
+ static_assert(!std::chrono::is_clock_v<std::chrono::seconds>);
+ static_assert(!std::chrono::is_clock_v<std::chrono::milliseconds>);
+
+ // Test structs missing required members
+ static_assert(!std::chrono::is_clock_v<MissingRep>);
+ static_assert(!std::chrono::is_clock_v<MissingPeriod>);
+ static_assert(!std::chrono::is_clock_v<MissingDuration>);
+ static_assert(!std::chrono::is_clock_v<MissingTimePoint>);
+ static_assert(!std::chrono::is_clock_v<MissingIsSteady>);
+ static_assert(!std::chrono::is_clock_v<MissingNow>);
+
+ // Test valid custom clocks
+ static_assert(std::chrono::is_clock_v<ValidSteadyClock>);
+ static_assert(std::chrono::is_clock_v<ValidSystemClock>);
+
+ // cv-qualified and reference types
+ static_assert(std::chrono::is_clock_v<const std::chrono::system_clock>);
+ static_assert(std::chrono::is_clock_v<volatile std::chrono::system_clock>);
+ static_assert(std::chrono::is_clock_v<const volatile std::chrono::system_clock>);
+ static_assert(!std::chrono::is_clock_v<std::chrono::system_clock&>);
+ static_assert(!std::chrono::is_clock_v<std::chrono::system_clock&&>);
+ static_assert(!std::chrono::is_clock_v<const std::chrono::system_clock&>);
+
+ // array and pointer types
+ static_assert(!std::chrono::is_clock_v<std::chrono::system_clock[]>);
+ static_assert(!std::chrono::is_clock_v<std::chrono::system_clock[10]>);
+ static_assert(!std::chrono::is_clock_v<std::chrono::system_clock*>);
+ static_assert(!std::chrono::is_clock_v<std::chrono::system_clock* const>);
+
+ return 0;
+}
>From 5fcfd586294c01d03530bd67f8e726f93411bdac Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at fb.com>
Date: Wed, 24 Sep 2025 21:09:26 -0700
Subject: [PATCH 02/13] Apply suggestions in libcxx/include/__chrono/is_clock.h
Co-authored-by: A. Jiang <de34 at live.cn>
---
libcxx/include/__chrono/is_clock.h | 22 +++++++++-------------
1 file changed, 9 insertions(+), 13 deletions(-)
diff --git a/libcxx/include/__chrono/is_clock.h b/libcxx/include/__chrono/is_clock.h
index 877d31ad31176..fcebbf48a64c4 100644
--- a/libcxx/include/__chrono/is_clock.h
+++ b/libcxx/include/__chrono/is_clock.h
@@ -24,22 +24,18 @@ _LIBCPP_BEGIN_NAMESPACE_STD
namespace chrono {
-template <class>
-struct is_clock : std::false_type {};
-
template <class _Tp>
- requires requires {
- typename _Tp::rep;
- typename _Tp::period;
- typename _Tp::duration;
- typename _Tp::time_point;
- _Tp::is_steady;
- _Tp::now();
- }
-struct is_clock<_Tp> : std::true_type {};
+_LIBCPP_NO_SPECIALIZATIONS inline constexpr bool is_clock_v = requires {
+ typename _Tp::rep;
+ typename _Tp::period;
+ typename _Tp::duration;
+ typename _Tp::time_point;
+ _Tp::is_steady;
+ _Tp::now();
+};
template <class _Tp>
-_LIBCPP_NO_SPECIALIZATIONS inline constexpr bool is_clock_v = is_clock<_Tp>::value;
+struct _LIBCPP_NO_SPECIALIZATIONS is_clock : bool_constant<is_clock_v<_Tp>> {};
} // namespace chrono
>From 5c09a5d812019c776e95d18d60b1e4916a4e0689 Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at meta.com>
Date: Thu, 25 Sep 2025 11:16:05 -0700
Subject: [PATCH 03/13] address comments
---
libcxx/docs/ReleaseNotes/22.rst | 2 --
libcxx/include/__chrono/is_clock.h | 3 +--
libcxx/include/chrono | 3 +++
...ss.cpp => trait.is.clock.compile.pass.cpp} | 0
.../trait.is.clock.compile.verify.cpp | 22 +++++++++++++++++++
5 files changed, 26 insertions(+), 4 deletions(-)
rename libcxx/test/std/time/time.traits.is.clock/{trait.is.clock.pass.cpp => trait.is.clock.compile.pass.cpp} (100%)
create mode 100644 libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.verify.cpp
diff --git a/libcxx/docs/ReleaseNotes/22.rst b/libcxx/docs/ReleaseNotes/22.rst
index b4261e474a27b..509ead64ee525 100644
--- a/libcxx/docs/ReleaseNotes/22.rst
+++ b/libcxx/docs/ReleaseNotes/22.rst
@@ -41,8 +41,6 @@ Implemented Papers
- P2321R2: ``zip`` (`Github <https://llvm.org/PR105169>`__) (The paper is partially implemented. ``zip_transform_view``
is implemented in this release)
- P3168R2: Give ``std::optional`` Range Support (`Github <https://llvm.org/PR105430>`__)
-- P0355R7: ``std::chrono::is_clock`` and ``std::chrono::is_clock_v`` (`Github <https://llvm.org/PR160607>` __)
- (The paper is partially implemented. ``is_clock`` and ``is_clock_v`` is implemented in this release)
Improvements and New Features
-----------------------------
diff --git a/libcxx/include/__chrono/is_clock.h b/libcxx/include/__chrono/is_clock.h
index fcebbf48a64c4..da65788af8a3a 100644
--- a/libcxx/include/__chrono/is_clock.h
+++ b/libcxx/include/__chrono/is_clock.h
@@ -11,6 +11,7 @@
#define _LIBCPP___CHRONO_IS_CLOCK_H
#include <__config>
+#include <__type_traits/integral_constant.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
@@ -18,8 +19,6 @@
#if _LIBCPP_STD_VER >= 20
-# include <__type_traits/integral_constant.h>
-
_LIBCPP_BEGIN_NAMESPACE_STD
namespace chrono {
diff --git a/libcxx/include/chrono b/libcxx/include/chrono
index f3bb08ef386c9..aa4fc6218f962 100644
--- a/libcxx/include/chrono
+++ b/libcxx/include/chrono
@@ -218,6 +218,9 @@ template <class ToDuration, class Rep, class Period>
template <class ToDuration, class Rep, class Period>
constexpr ToDuration round(const duration<Rep, Period>& d); // C++17
+template <class T> struct is_clock; // C++20
+template <class T> inline constexpr bool is_clock_v = is_clock<T>::value; // C++20
+
// duration I/O
template<class charT, class traits, class Rep, class Period> // C++20
basic_ostream<charT, traits>&
diff --git a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.pass.cpp b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
similarity index 100%
rename from libcxx/test/std/time/time.traits.is.clock/trait.is.clock.pass.cpp
rename to libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
diff --git a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.verify.cpp b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.verify.cpp
new file mode 100644
index 0000000000000..f902f7423032a
--- /dev/null
+++ b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.verify.cpp
@@ -0,0 +1,22 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: std-at-least-c++20
+
+#include <chrono>
+#include <ratio>
+
+namespace std::chrono {
+// try adding specializations to is_clock
+template <>
+struct is_clock<int> : std::false_type {}; // expected-error@*:* {{'is_clock' cannot be specialized}}
+
+template <>
+constexpr bool is_clock_v<float> = false; // expected-error@*:* {{'is_clock_v' cannot be specialized}}
+
+}
>From 7f1ad78a0f6d82822d1215176b6957c534b243c7 Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at meta.com>
Date: Thu, 25 Sep 2025 11:21:46 -0700
Subject: [PATCH 04/13] only test steady_clock if a macro is set
---
.../time/time.traits.is.clock/trait.is.clock.compile.pass.cpp | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
index 1abdf255054b3..78473808a00e4 100644
--- a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
+++ b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
@@ -87,7 +87,9 @@ int main(int, char**) {
// Test standard clock types
static_assert(std::chrono::is_clock_v<std::chrono::system_clock>);
+#ifdef _LIBCPP_HAS_MONOTONIC_CLOCK
static_assert(std::chrono::is_clock_v<std::chrono::steady_clock>);
+#endif
static_assert(std::chrono::is_clock_v<std::chrono::high_resolution_clock>);
// Test non-clock types
@@ -95,7 +97,9 @@ int main(int, char**) {
static_assert(!std::chrono::is_clock_v<int>);
static_assert(!std::chrono::is_clock_v<void>);
static_assert(!std::chrono::is_clock_v<std::chrono::system_clock::time_point>);
+#ifdef _LIBCPP_HAS_MONOTONIC_CLOCK
static_assert(!std::chrono::is_clock_v<std::chrono::steady_clock::time_point>);
+#endif
static_assert(!std::chrono::is_clock_v<std::chrono::seconds>);
static_assert(!std::chrono::is_clock_v<std::chrono::milliseconds>);
>From 11329c13affdf825e68735ffaca67d462fbef585 Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at meta.com>
Date: Thu, 25 Sep 2025 11:56:54 -0700
Subject: [PATCH 05/13] format in test
---
.../time/time.traits.is.clock/trait.is.clock.compile.verify.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.verify.cpp b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.verify.cpp
index f902f7423032a..fff9941844ee5 100644
--- a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.verify.cpp
+++ b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.verify.cpp
@@ -19,4 +19,4 @@ struct is_clock<int> : std::false_type {}; // expected-error@*:* {{'is_clock' ca
template <>
constexpr bool is_clock_v<float> = false; // expected-error@*:* {{'is_clock_v' cannot be specialized}}
-}
+} // namespace std::chrono
>From bd7ca123e6e2b118242ed59919104760f49bcfc0 Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at meta.com>
Date: Thu, 25 Sep 2025 12:02:39 -0700
Subject: [PATCH 06/13] more strict checks
---
libcxx/include/__chrono/is_clock.h | 28 +++++
.../trait.is.clock.compile.pass.cpp | 111 +++++++++++++++++-
2 files changed, 138 insertions(+), 1 deletion(-)
diff --git a/libcxx/include/__chrono/is_clock.h b/libcxx/include/__chrono/is_clock.h
index da65788af8a3a..e6020700a297e 100644
--- a/libcxx/include/__chrono/is_clock.h
+++ b/libcxx/include/__chrono/is_clock.h
@@ -12,6 +12,8 @@
#include <__config>
#include <__type_traits/integral_constant.h>
+#include <__type_traits/is_arithmetic.h>
+#include <__type_traits/is_same.h>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
@@ -23,14 +25,40 @@ _LIBCPP_BEGIN_NAMESPACE_STD
namespace chrono {
+template <class _Rep, class _Period>
+class duration;
+
+template <class _Clock, class _Duration>
+class time_point;
+
+template <class _TimePoint, class _Clock>
+constexpr bool __is_valid_clock_time_point_v = false;
+
+template <class _Clock, class _Duration, class _ClockType>
+constexpr bool __is_valid_clock_time_point_v<time_point<_Clock, _Duration>, _ClockType> =
+ _IsSame<time_point<_Clock, _Duration>, time_point<_ClockType>>::value ||
+ _IsSame<_Duration, typename _ClockType::duration>::value;
+
+// Check if a clock satisfies the Cpp17Clock requirements as defined in [time.clock.req]
template <class _Tp>
_LIBCPP_NO_SPECIALIZATIONS inline constexpr bool is_clock_v = requires {
typename _Tp::rep;
+ requires is_arithmetic_v<typename _Tp::rep>;
+
typename _Tp::period;
+ requires __is_ratio_v<typename _Tp::period>;
+
typename _Tp::duration;
+ requires _IsSame<typename _Tp::duration, duration<typename _Tp::rep, typename _Tp::period>>::value;
+
typename _Tp::time_point;
+ requires __is_valid_clock_time_point_v<typename _Tp::time_point, _Tp>;
+
_Tp::is_steady;
+ requires _IsSame<decltype(_Tp::is_steady), const bool>::value;
+
_Tp::now();
+ requires _IsSame<decltype(_Tp::now()), typename _Tp::time_point>::value;
};
template <class _Tp>
diff --git a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
index 78473808a00e4..f6e73bd288d0b 100644
--- a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
+++ b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
@@ -72,7 +72,7 @@ struct ValidSteadyClock {
};
struct ValidSystemClock {
- using rep = int64_t;
+ using rep = long long;
using period = std::micro;
using duration = std::chrono::microseconds;
using time_point = std::chrono::time_point<ValidSystemClock>;
@@ -80,6 +80,94 @@ struct ValidSystemClock {
static time_point now();
};
+// Test clocks with invalid is_steady type
+struct WrongIsSteadyType {
+ using rep = long;
+ using period = std::ratio<1>;
+ using duration = std::chrono::seconds;
+ using time_point = std::chrono::time_point<WrongIsSteadyType>;
+ static bool is_steady; // Not const bool
+ static time_point now();
+};
+
+struct WrongIsSteadyNonBool {
+ using rep = long;
+ using period = std::ratio<1>;
+ using duration = std::chrono::seconds;
+ using time_point = std::chrono::time_point<WrongIsSteadyNonBool>;
+ static constexpr int is_steady = 1; // Not bool
+ static time_point now();
+};
+
+// Test clocks with invalid now() return type
+struct WrongNowReturnType {
+ using rep = long;
+ using period = std::ratio<1>;
+ using duration = std::chrono::seconds;
+ using time_point = std::chrono::time_point<WrongNowReturnType>;
+ static constexpr bool is_steady = false;
+ static int now(); // Wrong return type
+};
+
+// Test clocks with invalid period type
+struct WrongPeriodType {
+ using rep = long;
+ using period = int; // Not a ratio
+ using duration = std::chrono::seconds;
+ using time_point = std::chrono::time_point<WrongPeriodType>;
+ static constexpr bool is_steady = false;
+ static time_point now();
+};
+
+// Test clocks with invalid rep type (neither arithmetic nor numeric_limits specialized)
+struct InvalidRepType {
+ using rep = EmptyStruct; // Not arithmetic, no numeric_limits specialization
+ using period = std::ratio<1>;
+ using duration = std::chrono::duration<EmptyStruct>;
+ using time_point = std::chrono::time_point<InvalidRepType, duration>;
+ static constexpr bool is_steady = false;
+ static time_point now();
+};
+
+// Test clocks with wrong duration type
+struct WrongDurationType {
+ using rep = long;
+ using period = std::ratio<1>;
+ using duration = std::chrono::milliseconds; // Should be duration<long, ratio<1>>
+ using time_point = std::chrono::time_point<WrongDurationType>;
+ static constexpr bool is_steady = false;
+ static time_point now();
+};
+
+// Test clocks with wrong time_point type
+struct WrongTimePointType {
+ using rep = long;
+ using period = std::ratio<1>;
+ using duration = std::chrono::duration<long, std::ratio<1>>;
+ using time_point = int; // Not a time_point
+ static constexpr bool is_steady = false;
+ static time_point now();
+};
+
+struct WrongTimePointClock {
+ using rep = long;
+ using period = std::ratio<1>;
+ using duration = std::chrono::duration<long, std::ratio<1>>;
+ using time_point = std::chrono::time_point<ValidSystemClock>; // Wrong clock type
+ static constexpr bool is_steady = false;
+ static time_point now();
+};
+
+// Valid clock with time_point that has matching duration instead of matching clock
+struct ValidClockWithDurationMatch {
+ using rep = int;
+ using period = std::milli;
+ using duration = std::chrono::duration<int, std::milli>;
+ using time_point = std::chrono::time_point<ValidSystemClock, duration>; // Valid: matches duration
+ static constexpr bool is_steady = false;
+ static time_point now();
+};
+
int main(int, char**) {
// Test both is_clock and is_clock_v
static_assert(std::chrono::is_clock<std::chrono::system_clock>::value);
@@ -114,6 +202,27 @@ int main(int, char**) {
// Test valid custom clocks
static_assert(std::chrono::is_clock_v<ValidSteadyClock>);
static_assert(std::chrono::is_clock_v<ValidSystemClock>);
+ static_assert(std::chrono::is_clock_v<ValidClockWithDurationMatch>);
+
+ // Test clocks with invalid is_steady type
+ static_assert(!std::chrono::is_clock_v<WrongIsSteadyType>); // is_steady not const bool
+ static_assert(!std::chrono::is_clock_v<WrongIsSteadyNonBool>); // is_steady not bool type
+
+ // Test clocks with invalid now() return type
+ static_assert(!std::chrono::is_clock_v<WrongNowReturnType>); // now() doesn't return time_point
+
+ // Test clocks with invalid period type
+ static_assert(!std::chrono::is_clock_v<WrongPeriodType>); // period is not a ratio
+
+ // Test clocks with invalid rep type
+ static_assert(!std::chrono::is_clock_v<InvalidRepType>); // rep is not arithmetic and no numeric_limits
+
+ // Test clocks with wrong duration type
+ static_assert(!std::chrono::is_clock_v<WrongDurationType>); // duration doesn't match duration<rep, period>
+
+ // Test clocks with wrong time_point type
+ static_assert(!std::chrono::is_clock_v<WrongTimePointType>); // time_point is not a time_point
+ static_assert(!std::chrono::is_clock_v<WrongTimePointClock>); // time_point has wrong clock and wrong duration
// cv-qualified and reference types
static_assert(std::chrono::is_clock_v<const std::chrono::system_clock>);
>From 12a38fb1a2abdbcd63f708466cee39cb81ab94da Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at meta.com>
Date: Fri, 26 Sep 2025 10:47:59 -0700
Subject: [PATCH 07/13] apply suggestions to test file
---
.../trait.is.clock.compile.pass.cpp | 134 +++++++++---------
1 file changed, 68 insertions(+), 66 deletions(-)
diff --git a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
index f6e73bd288d0b..a918abed882cf 100644
--- a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
+++ b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
@@ -11,6 +11,8 @@
#include <chrono>
#include <ratio>
+#include "test_macros.h"
+
struct EmptyStruct {};
// Test structs missing required members
@@ -168,75 +170,75 @@ struct ValidClockWithDurationMatch {
static time_point now();
};
-int main(int, char**) {
- // Test both is_clock and is_clock_v
- static_assert(std::chrono::is_clock<std::chrono::system_clock>::value);
- static_assert(std::chrono::is_clock_v<std::chrono::system_clock>);
+// Test both is_clock and is_clock_v
+static_assert(std::chrono::is_clock<std::chrono::system_clock>::value);
+static_assert(std::chrono::is_clock_v<std::chrono::system_clock>);
- // Test standard clock types
- static_assert(std::chrono::is_clock_v<std::chrono::system_clock>);
+// Test standard clock types
+static_assert(std::chrono::is_clock_v<std::chrono::system_clock>);
#ifdef _LIBCPP_HAS_MONOTONIC_CLOCK
- static_assert(std::chrono::is_clock_v<std::chrono::steady_clock>);
+static_assert(std::chrono::is_clock_v<std::chrono::steady_clock>);
#endif
- static_assert(std::chrono::is_clock_v<std::chrono::high_resolution_clock>);
+static_assert(std::chrono::is_clock_v<std::chrono::high_resolution_clock>);
- // Test non-clock types
- static_assert(!std::chrono::is_clock_v<EmptyStruct>);
- static_assert(!std::chrono::is_clock_v<int>);
- static_assert(!std::chrono::is_clock_v<void>);
- static_assert(!std::chrono::is_clock_v<std::chrono::system_clock::time_point>);
+// Test non-clock types
+static_assert(!std::chrono::is_clock_v<EmptyStruct>);
+static_assert(!std::chrono::is_clock_v<int>);
+static_assert(!std::chrono::is_clock_v<void>);
+static_assert(!std::chrono::is_clock_v<std::chrono::system_clock::time_point>);
#ifdef _LIBCPP_HAS_MONOTONIC_CLOCK
- static_assert(!std::chrono::is_clock_v<std::chrono::steady_clock::time_point>);
+static_assert(!std::chrono::is_clock_v<std::chrono::steady_clock::time_point>);
#endif
- static_assert(!std::chrono::is_clock_v<std::chrono::seconds>);
- static_assert(!std::chrono::is_clock_v<std::chrono::milliseconds>);
-
- // Test structs missing required members
- static_assert(!std::chrono::is_clock_v<MissingRep>);
- static_assert(!std::chrono::is_clock_v<MissingPeriod>);
- static_assert(!std::chrono::is_clock_v<MissingDuration>);
- static_assert(!std::chrono::is_clock_v<MissingTimePoint>);
- static_assert(!std::chrono::is_clock_v<MissingIsSteady>);
- static_assert(!std::chrono::is_clock_v<MissingNow>);
-
- // Test valid custom clocks
- static_assert(std::chrono::is_clock_v<ValidSteadyClock>);
- static_assert(std::chrono::is_clock_v<ValidSystemClock>);
- static_assert(std::chrono::is_clock_v<ValidClockWithDurationMatch>);
-
- // Test clocks with invalid is_steady type
- static_assert(!std::chrono::is_clock_v<WrongIsSteadyType>); // is_steady not const bool
- static_assert(!std::chrono::is_clock_v<WrongIsSteadyNonBool>); // is_steady not bool type
-
- // Test clocks with invalid now() return type
- static_assert(!std::chrono::is_clock_v<WrongNowReturnType>); // now() doesn't return time_point
-
- // Test clocks with invalid period type
- static_assert(!std::chrono::is_clock_v<WrongPeriodType>); // period is not a ratio
-
- // Test clocks with invalid rep type
- static_assert(!std::chrono::is_clock_v<InvalidRepType>); // rep is not arithmetic and no numeric_limits
-
- // Test clocks with wrong duration type
- static_assert(!std::chrono::is_clock_v<WrongDurationType>); // duration doesn't match duration<rep, period>
-
- // Test clocks with wrong time_point type
- static_assert(!std::chrono::is_clock_v<WrongTimePointType>); // time_point is not a time_point
- static_assert(!std::chrono::is_clock_v<WrongTimePointClock>); // time_point has wrong clock and wrong duration
-
- // cv-qualified and reference types
- static_assert(std::chrono::is_clock_v<const std::chrono::system_clock>);
- static_assert(std::chrono::is_clock_v<volatile std::chrono::system_clock>);
- static_assert(std::chrono::is_clock_v<const volatile std::chrono::system_clock>);
- static_assert(!std::chrono::is_clock_v<std::chrono::system_clock&>);
- static_assert(!std::chrono::is_clock_v<std::chrono::system_clock&&>);
- static_assert(!std::chrono::is_clock_v<const std::chrono::system_clock&>);
-
- // array and pointer types
- static_assert(!std::chrono::is_clock_v<std::chrono::system_clock[]>);
- static_assert(!std::chrono::is_clock_v<std::chrono::system_clock[10]>);
- static_assert(!std::chrono::is_clock_v<std::chrono::system_clock*>);
- static_assert(!std::chrono::is_clock_v<std::chrono::system_clock* const>);
-
- return 0;
-}
+static_assert(!std::chrono::is_clock_v<std::chrono::seconds>);
+static_assert(!std::chrono::is_clock_v<std::chrono::milliseconds>);
+
+// Test structs missing required members
+static_assert(!std::chrono::is_clock_v<MissingRep>);
+static_assert(!std::chrono::is_clock_v<MissingPeriod>);
+static_assert(!std::chrono::is_clock_v<MissingDuration>);
+static_assert(!std::chrono::is_clock_v<MissingTimePoint>);
+static_assert(!std::chrono::is_clock_v<MissingIsSteady>);
+static_assert(!std::chrono::is_clock_v<MissingNow>);
+
+// Test valid custom clocks
+static_assert(std::chrono::is_clock_v<ValidSteadyClock>);
+static_assert(std::chrono::is_clock_v<ValidSystemClock>);
+static_assert(std::chrono::is_clock_v<ValidClockWithDurationMatch>);
+
+// cv-qualified and reference types
+static_assert(std::chrono::is_clock_v<const std::chrono::system_clock>);
+static_assert(std::chrono::is_clock_v<volatile std::chrono::system_clock>);
+static_assert(std::chrono::is_clock_v<const volatile std::chrono::system_clock>);
+static_assert(!std::chrono::is_clock_v<std::chrono::system_clock&>);
+static_assert(!std::chrono::is_clock_v<std::chrono::system_clock&&>);
+static_assert(!std::chrono::is_clock_v<const std::chrono::system_clock&>);
+
+// array and pointer types
+static_assert(!std::chrono::is_clock_v<std::chrono::system_clock[]>);
+static_assert(!std::chrono::is_clock_v<std::chrono::system_clock[10]>);
+static_assert(!std::chrono::is_clock_v<std::chrono::system_clock*>);
+static_assert(!std::chrono::is_clock_v<std::chrono::system_clock* const>);
+
+// The Standard defined a minimum set of checks and allowed implementation to perform stricter checks. The following
+// static asserts are implementation specific and a conforming standard library implementation doesn't have to produce
+// the same outcome.
+
+// Test clocks with invalid is_steady type
+LIBCPP_STATIC_ASSERT(!std::chrono::is_clock_v<WrongIsSteadyType>); // is_steady not const bool
+LIBCPP_STATIC_ASSERT(!std::chrono::is_clock_v<WrongIsSteadyNonBool>); // is_steady not bool type
+
+// Test clocks with invalid now() return type
+LIBCPP_STATIC_ASSERT(!std::chrono::is_clock_v<WrongNowReturnType>); // now() doesn't return time_point
+
+// Test clocks with invalid period type
+LIBCPP_STATIC_ASSERT(!std::chrono::is_clock_v<WrongPeriodType>); // period is not a ratio
+
+// Test clocks with invalid rep type
+LIBCPP_STATIC_ASSERT(!std::chrono::is_clock_v<InvalidRepType>); // rep is not arithmetic and no numeric_limits
+
+// Test clocks with wrong duration type
+LIBCPP_STATIC_ASSERT(!std::chrono::is_clock_v<WrongDurationType>); // duration doesn't match duration<rep, period>
+
+// Test clocks with wrong time_point type
+LIBCPP_STATIC_ASSERT(!std::chrono::is_clock_v<WrongTimePointType>); // time_point is not a time_point
+LIBCPP_STATIC_ASSERT(!std::chrono::is_clock_v<WrongTimePointClock>); // time_point has wrong clock and wrong duration
>From 3af9f2dced94652e35fa4575a74bad7322a52ce4 Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at meta.com>
Date: Fri, 26 Sep 2025 11:05:03 -0700
Subject: [PATCH 08/13] simplify time_point checks
---
libcxx/include/__chrono/is_clock.h | 10 +---------
1 file changed, 1 insertion(+), 9 deletions(-)
diff --git a/libcxx/include/__chrono/is_clock.h b/libcxx/include/__chrono/is_clock.h
index e6020700a297e..463369a65e9db 100644
--- a/libcxx/include/__chrono/is_clock.h
+++ b/libcxx/include/__chrono/is_clock.h
@@ -31,14 +31,6 @@ class duration;
template <class _Clock, class _Duration>
class time_point;
-template <class _TimePoint, class _Clock>
-constexpr bool __is_valid_clock_time_point_v = false;
-
-template <class _Clock, class _Duration, class _ClockType>
-constexpr bool __is_valid_clock_time_point_v<time_point<_Clock, _Duration>, _ClockType> =
- _IsSame<time_point<_Clock, _Duration>, time_point<_ClockType>>::value ||
- _IsSame<_Duration, typename _ClockType::duration>::value;
-
// Check if a clock satisfies the Cpp17Clock requirements as defined in [time.clock.req]
template <class _Tp>
_LIBCPP_NO_SPECIALIZATIONS inline constexpr bool is_clock_v = requires {
@@ -52,7 +44,7 @@ _LIBCPP_NO_SPECIALIZATIONS inline constexpr bool is_clock_v = requires {
requires _IsSame<typename _Tp::duration, duration<typename _Tp::rep, typename _Tp::period>>::value;
typename _Tp::time_point;
- requires __is_valid_clock_time_point_v<typename _Tp::time_point, _Tp>;
+ requires _IsSame<typename _Tp::time_point::duration, typename _Tp::duration>::value;
_Tp::is_steady;
requires _IsSame<decltype(_Tp::is_steady), const bool>::value;
>From 5340360c850a8274a494b7a913f6e02706970398 Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at meta.com>
Date: Fri, 26 Sep 2025 11:28:03 -0700
Subject: [PATCH 09/13] include <ratio>
---
libcxx/include/__chrono/is_clock.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/libcxx/include/__chrono/is_clock.h b/libcxx/include/__chrono/is_clock.h
index 463369a65e9db..235c6004ef253 100644
--- a/libcxx/include/__chrono/is_clock.h
+++ b/libcxx/include/__chrono/is_clock.h
@@ -14,6 +14,7 @@
#include <__type_traits/integral_constant.h>
#include <__type_traits/is_arithmetic.h>
#include <__type_traits/is_same.h>
+#include <ratio>
#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
# pragma GCC system_header
>From 4afb48af7018316ffc749b1a77167d8cb0e70798 Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at meta.com>
Date: Fri, 26 Sep 2025 12:05:42 -0700
Subject: [PATCH 10/13] fix AIX CI
---
.../time.traits.is.clock/trait.is.clock.compile.verify.cpp | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.verify.cpp b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.verify.cpp
index fff9941844ee5..963ba34667416 100644
--- a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.verify.cpp
+++ b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.verify.cpp
@@ -11,6 +11,10 @@
#include <chrono>
#include <ratio>
+#if !__has_warning("-Winvalid-specializations")
+// expected-no-diagnostics
+#else
+
namespace std::chrono {
// try adding specializations to is_clock
template <>
@@ -20,3 +24,5 @@ template <>
constexpr bool is_clock_v<float> = false; // expected-error@*:* {{'is_clock_v' cannot be specialized}}
} // namespace std::chrono
+
+#endif
>From 4a01d77a04aefc109487b3ffd08b9944c7e64120 Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at meta.com>
Date: Mon, 29 Sep 2025 09:13:54 -0700
Subject: [PATCH 11/13] fix monotonic clock check
---
.../time/time.traits.is.clock/trait.is.clock.compile.pass.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
index a918abed882cf..e62dbffa08349 100644
--- a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
+++ b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
@@ -176,7 +176,7 @@ static_assert(std::chrono::is_clock_v<std::chrono::system_clock>);
// Test standard clock types
static_assert(std::chrono::is_clock_v<std::chrono::system_clock>);
-#ifdef _LIBCPP_HAS_MONOTONIC_CLOCK
+#if _LIBCPP_HAS_MONOTONIC_CLOCK
static_assert(std::chrono::is_clock_v<std::chrono::steady_clock>);
#endif
static_assert(std::chrono::is_clock_v<std::chrono::high_resolution_clock>);
>From 89223a8cd4a6fd9482b7f86c437da4e21c0861e5 Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at meta.com>
Date: Mon, 29 Sep 2025 09:30:35 -0700
Subject: [PATCH 12/13] still check for specialization
---
libcxx/include/__chrono/is_clock.h | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/libcxx/include/__chrono/is_clock.h b/libcxx/include/__chrono/is_clock.h
index 235c6004ef253..7afc7aa861d05 100644
--- a/libcxx/include/__chrono/is_clock.h
+++ b/libcxx/include/__chrono/is_clock.h
@@ -32,6 +32,14 @@ class duration;
template <class _Clock, class _Duration>
class time_point;
+// Helper to check that _Tp::time_point has the form time_point<_, typename _Tp::duration>.
+template <class _TimePoint, class _ClockType>
+constexpr bool __is_valid_clock_time_point_v = false;
+
+template <class _TimePointClock, class _ClockType>
+constexpr bool __is_valid_clock_time_point_v<time_point<_TimePointClock, typename _ClockType::duration>, _ClockType> =
+ true;
+
// Check if a clock satisfies the Cpp17Clock requirements as defined in [time.clock.req]
template <class _Tp>
_LIBCPP_NO_SPECIALIZATIONS inline constexpr bool is_clock_v = requires {
@@ -45,7 +53,7 @@ _LIBCPP_NO_SPECIALIZATIONS inline constexpr bool is_clock_v = requires {
requires _IsSame<typename _Tp::duration, duration<typename _Tp::rep, typename _Tp::period>>::value;
typename _Tp::time_point;
- requires _IsSame<typename _Tp::time_point::duration, typename _Tp::duration>::value;
+ requires __is_valid_clock_time_point_v<typename _Tp::time_point, _Tp>;
_Tp::is_steady;
requires _IsSame<decltype(_Tp::is_steady), const bool>::value;
>From 6f7a8a66502884b6c0bd167e616e080bfaef3b9e Mon Sep 17 00:00:00 2001
From: Yuxuan Chen <ych at meta.com>
Date: Tue, 30 Sep 2025 10:43:37 -0700
Subject: [PATCH 13/13] fix if _LIBCPP_HAS_MONOTONIC_CLOCK
---
.../time/time.traits.is.clock/trait.is.clock.compile.pass.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
index e62dbffa08349..76c3249626fcb 100644
--- a/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
+++ b/libcxx/test/std/time/time.traits.is.clock/trait.is.clock.compile.pass.cpp
@@ -186,7 +186,7 @@ static_assert(!std::chrono::is_clock_v<EmptyStruct>);
static_assert(!std::chrono::is_clock_v<int>);
static_assert(!std::chrono::is_clock_v<void>);
static_assert(!std::chrono::is_clock_v<std::chrono::system_clock::time_point>);
-#ifdef _LIBCPP_HAS_MONOTONIC_CLOCK
+#if _LIBCPP_HAS_MONOTONIC_CLOCK
static_assert(!std::chrono::is_clock_v<std::chrono::steady_clock::time_point>);
#endif
static_assert(!std::chrono::is_clock_v<std::chrono::seconds>);
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