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libstdc++: Invert relationship between std::is_clock and std::is_clock_v 

This redefines std::is_clock in terms of std::is_clock_v, instead of the
other way around. This avoids instantiatng the class template for code
that only uses the variable template.

libstdc++-v3/ChangeLog:

	* include/bits/chrono.h (is_clock_v): Define to false.
	(is_clock_v<T>): Define partial specialization for true cases.
	(is_clock): Define in terms of is_clock_v.
This commit is contained in:
Jonathan Wakely 2022-06-23 18:17:30 +01:00
parent 153689603f
commit 48099f7daf
1 changed files with 20 additions and 29 deletions
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49
libstdc++-v3/include/bits/chrono.h
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@ -273,16 +273,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
#endif // C++17
#if __cplusplus > 201703L
template<typename _Tp>
struct is_clock;
template<typename _Tp>
inline constexpr bool is_clock_v = is_clock<_Tp>::value;
#if __cpp_lib_concepts
template<typename _Tp>
struct is_clock : false_type
{ };
inline constexpr bool is_clock_v = false;
template<typename _Tp>
requires requires {
@ -298,32 +291,30 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
requires same_as<typename _Tp::time_point::duration,
typename _Tp::duration>;
}
struct is_clock<_Tp> : true_type
{ };
inline constexpr bool is_clock_v<_Tp> = true;
#else
template<typename _Tp, typename = void>
struct __is_clock_impl : false_type
{ };
inline constexpr bool is_clock_v = false;
template<typename _Tp>
struct __is_clock_impl<_Tp,
void_t<typename _Tp::rep, typename _Tp::period,
typename _Tp::duration,
typename _Tp::time_point::duration,
decltype(_Tp::is_steady),
decltype(_Tp::now())>>
: __and_<is_same<typename _Tp::duration,
duration<typename _Tp::rep, typename _Tp::period>>,
is_same<typename _Tp::time_point::duration,
typename _Tp::duration>,
is_same<decltype(&_Tp::is_steady), const bool*>,
is_same<decltype(_Tp::now()), typename _Tp::time_point>>::type
{ };
template<typename _Tp>
struct is_clock : __is_clock_impl<_Tp>::type
{ };
inline constexpr bool
is_clock_v<_Tp, void_t<typename _Tp::rep, typename _Tp::period,
typename _Tp::duration,
typename _Tp::time_point::duration,
decltype(_Tp::is_steady),
decltype(_Tp::now())>>
= __and_v<is_same<typename _Tp::duration,
duration<typename _Tp::rep, typename _Tp::period>>,
is_same<typename _Tp::time_point::duration,
typename _Tp::duration>,
is_same<decltype(&_Tp::is_steady), const bool*>,
is_same<decltype(_Tp::now()), typename _Tp::time_point>>;
#endif
template<typename _Tp>
struct is_clock
: bool_constant<is_clock_v<_Tp>>
{ };
#endif // C++20
#if __cplusplus >= 201703L