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* [gcc r13-4572] libstdc++: Add [[nodiscard]] to chrono conversion functions
@ 2022-12-09 0:35 Jonathan Wakely
0 siblings, 0 replies; only message in thread
From: Jonathan Wakely @ 2022-12-09 0:35 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:646e979c43b8c84f0f70ea8f1709dfa2909726cd
commit r13-4572-g646e979c43b8c84f0f70ea8f1709dfa2909726cd
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Mon Nov 28 11:22:24 2022 +0000
libstdc++: Add [[nodiscard]] to chrono conversion functions
Also add doxygen comments.
libstdc++-v3/ChangeLog:
* include/bits/chrono.h (duration_cast, floor, round, abs, ceil)
(time_point_cast): Add [[nodiscard]] attribute and doxygen
comments.
(treat_as_floating_point): Add doxygen commen.
Diff:
---
libstdc++-v3/include/bits/chrono.h | 139 ++++++++++++++++++++++++++++++++-----
1 file changed, 123 insertions(+), 16 deletions(-)
diff --git a/libstdc++-v3/include/bits/chrono.h b/libstdc++-v3/include/bits/chrono.h
index 496e9485a73..22c0be3fbe6 100644
--- a/libstdc++-v3/include/bits/chrono.h
+++ b/libstdc++-v3/include/bits/chrono.h
@@ -246,8 +246,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
/// @endcond
- /// duration_cast
+ /** Convert a `duration` to type `ToDur`.
+ *
+ * If the duration cannot be represented accurately in the result type,
+ * returns the result of integer truncation (i.e., rounded towards zero).
+ *
+ * @tparam _ToDur The result type must be a `duration`.
+ * @param __d A duration.
+ * @return The value of `__d` converted to type `_ToDur`.
+ * @since C++11
+ */
template<typename _ToDur, typename _Rep, typename _Period>
+ _GLIBCXX_NODISCARD
constexpr __enable_if_is_duration<_ToDur>
duration_cast(const duration<_Rep, _Period>& __d)
{
@@ -260,7 +270,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return __dc::__cast(__d);
}
- /// treat_as_floating_point
+ /** Trait indicating whether to treat a type as a floating-point type.
+ *
+ * The chrono library uses this trait to tell whether a `duration` can
+ * represent fractional values of the given precision, or only integral
+ * values.
+ *
+ * You should specialize this trait for your own numeric types that are
+ * used with `duration` and can represent non-integral values.
+ *
+ * @since C++11
+ */
template<typename _Rep>
struct treat_as_floating_point
: is_floating_point<_Rep>
@@ -320,8 +340,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#if __cplusplus >= 201703L
# define __cpp_lib_chrono 201611L
+ /** Convert a `duration` to type `ToDur` and round down.
+ *
+ * If the duration cannot be represented exactly in the result type,
+ * returns the closest value that is less than the argument.
+ *
+ * @tparam _ToDur The result type must be a `duration`.
+ * @param __d A duration.
+ * @return The value of `__d` converted to type `_ToDur`.
+ * @since C++17
+ */
template<typename _ToDur, typename _Rep, typename _Period>
- constexpr __enable_if_is_duration<_ToDur>
+ [[nodiscard]] constexpr __enable_if_is_duration<_ToDur>
floor(const duration<_Rep, _Period>& __d)
{
auto __to = chrono::duration_cast<_ToDur>(__d);
@@ -330,8 +360,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return __to;
}
+ /** Convert a `duration` to type `ToDur` and round up.
+ *
+ * If the duration cannot be represented exactly in the result type,
+ * returns the closest value that is greater than the argument.
+ *
+ * @tparam _ToDur The result type must be a `duration`.
+ * @param __d A duration.
+ * @return The value of `__d` converted to type `_ToDur`.
+ * @since C++17
+ */
template<typename _ToDur, typename _Rep, typename _Period>
- constexpr __enable_if_is_duration<_ToDur>
+ [[nodiscard]] constexpr __enable_if_is_duration<_ToDur>
ceil(const duration<_Rep, _Period>& __d)
{
auto __to = chrono::duration_cast<_ToDur>(__d);
@@ -340,8 +380,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return __to;
}
+ /** Convert a `duration` to type `ToDur` and round to the closest value.
+ *
+ * If the duration cannot be represented exactly in the result type,
+ * returns the closest value, rounding ties to even.
+ *
+ * @tparam _ToDur The result type must be a `duration` with a
+ * non-floating-point `rep` type.
+ * @param __d A duration.
+ * @return The value of `__d` converted to type `_ToDur`.
+ * @since C++17
+ */
template <typename _ToDur, typename _Rep, typename _Period>
- constexpr enable_if_t<
+ [[nodiscard]] constexpr
+ enable_if_t<
__and_<__is_duration<_ToDur>,
__not_<treat_as_floating_point<typename _ToDur::rep>>>::value,
_ToDur>
@@ -352,18 +404,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
auto __diff0 = __d - __t0;
auto __diff1 = __t1 - __d;
if (__diff0 == __diff1)
- {
+ {
if (__t0.count() & 1)
- return __t1;
+ return __t1;
return __t0;
- }
+ }
else if (__diff0 < __diff1)
- return __t0;
+ return __t0;
return __t1;
}
+ /** The absolute (non-negative) value of a duration.
+ *
+ * @param __d A duration with a signed `rep` type.
+ * @return A duration of the same type as the argument, with value |d|.
+ * @since C++17
+ */
template<typename _Rep, typename _Period>
- constexpr
+ [[nodiscard]] constexpr
enable_if_t<numeric_limits<_Rep>::is_signed, duration<_Rep, _Period>>
abs(duration<_Rep, _Period> __d)
{
@@ -925,10 +983,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
duration __d;
};
- /// time_point_cast
+ /** Convert a `time_point` to use `duration` type `ToDur`.
+ *
+ * The result is the same time point as measured by the same clock, but
+ * using the specified `duration` to represent the time.
+ * If the time point cannot be represented accurately in the result type,
+ * returns the result of integer truncation (i.e., rounded towards zero).
+ *
+ * @tparam _ToDur The `duration` type to use for the result.
+ * @param __t A time point.
+ * @return The value of `__t` converted to use type `_ToDur`.
+ * @since C++11
+ */
template<typename _ToDur, typename _Clock, typename _Dur>
- constexpr typename enable_if<__is_duration<_ToDur>::value,
- time_point<_Clock, _ToDur>>::type
+ _GLIBCXX_NODISCARD constexpr
+ __enable_if_t<__is_duration<_ToDur>::value, time_point<_Clock, _ToDur>>
time_point_cast(const time_point<_Clock, _Dur>& __t)
{
typedef time_point<_Clock, _ToDur> __time_point;
@@ -936,8 +1005,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
#if __cplusplus > 201402L
+ /** Convert a `time_point` to type `ToDur` and round down.
+ *
+ * The result is the same time point as measured by the same clock, but
+ * using the specified `duration` to represent the time.
+ * If the time point cannot be represented exactly in the result type,
+ * returns the closest value that is less than the argument.
+ *
+ * @tparam _ToDur The `duration` type to use for the result.
+ * @param __t A time point.
+ * @return The value of `__d` converted to type `_ToDur`.
+ * @since C++17
+ */
template<typename _ToDur, typename _Clock, typename _Dur>
- constexpr
+ [[nodiscard]] constexpr
enable_if_t<__is_duration<_ToDur>::value, time_point<_Clock, _ToDur>>
floor(const time_point<_Clock, _Dur>& __tp)
{
@@ -945,8 +1026,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
chrono::floor<_ToDur>(__tp.time_since_epoch())};
}
+ /** Convert a `time_point` to type `ToDur` and round up.
+ *
+ * The result is the same time point as measured by the same clock, but
+ * using the specified `duration` to represent the time.
+ * If the time point cannot be represented exactly in the result type,
+ * returns the closest value that is greater than the argument.
+ *
+ * @tparam _ToDur The `duration` type to use for the result.
+ * @param __t A time point.
+ * @return The value of `__d` converted to type `_ToDur`.
+ * @since C++17
+ */
template<typename _ToDur, typename _Clock, typename _Dur>
- constexpr
+ [[nodiscard]] constexpr
enable_if_t<__is_duration<_ToDur>::value, time_point<_Clock, _ToDur>>
ceil(const time_point<_Clock, _Dur>& __tp)
{
@@ -954,8 +1047,22 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
chrono::ceil<_ToDur>(__tp.time_since_epoch())};
}
+ /** Convert a `time_point` to type `ToDur` and round to the closest value.
+ *
+ * The result is the same time point as measured by the same clock, but
+ * using the specified `duration` to represent the time.
+ * If the time point cannot be represented exactly in the result type,
+ * returns the closest value, rounding ties to even.
+ *
+ * @tparam _ToDur The `duration` type to use for the result,
+ * which must have a non-floating-point `rep` type.
+ * @param __t A time point.
+ * @return The value of `__d` converted to type `_ToDur`.
+ * @since C++17
+ */
template<typename _ToDur, typename _Clock, typename _Dur>
- constexpr enable_if_t<
+ [[nodiscard]] constexpr
+ enable_if_t<
__and_<__is_duration<_ToDur>,
__not_<treat_as_floating_point<typename _ToDur::rep>>>::value,
time_point<_Clock, _ToDur>>
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