[PATCH] Implement LWG 3062, Unnecessary decay_t in is_execution_policy_v

[Thomas Rodgers]

Revised patch.

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Jonathan Wakely writes:

> On 24/04/19 16:01 -0700, Thomas Rodgers wrote:
>>
>>	should be remove_cvref_t
>>	* include/pstl/execution_defs.h (__enable_if_execution_policy):
>>        Use std::__remove_cv_ref_t when building with GCC
>>
>
>>From cb7bd9a39acacbf81df0d03da8714fa463057cc5 Mon Sep 17 00:00:00 2001
>>From: Thomas Rodgers <trodgers@redhat.com>
>>Date: Wed, 24 Apr 2019 15:53:45 -0700
>>Subject: [PATCH] Implement LWG 3062, Unnecessary decay_t in
>> is_execution_policy_v
>>
>>	should be remove_cvref_t
>>	* include/pstl/execution_defs.h (__enable_if_execution_policy):
>>        Use std::__remove_cv_ref_t when building with GCC.
>>---
>> libstdc++-v3/include/pstl/execution_defs.h | 6 ++++++
>> 1 file changed, 6 insertions(+)
>>
>>diff --git a/libstdc++-v3/include/pstl/execution_defs.h b/libstdc++-v3/include/pstl/execution_defs.h
>>index 86c7a5a770d..9b9b212b1bd 100644
>>--- a/libstdc++-v3/include/pstl/execution_defs.h
>>+++ b/libstdc++-v3/include/pstl/execution_defs.h
>>@@ -152,9 +152,15 @@ constexpr bool is_execution_policy_v = __pstl::execution::is_execution_policy<_T
>> namespace __internal
>> {
>> template <class _ExecPolicy, class _T>
>>+#if __GNUC__
>
> Clang and Intel both define that macro, but that doesn't mean
> __remove_cvref_t is available. I think you want __GLIBCXX__ to tell
> that libstdc++ is in use, or better still:
>
> #if _GLIBCXX_RELEASE >= 9
>
>>+using __enable_if_execution_policy =
>>+    typename std::enable_if<__pstl::execution::is_execution_policy<typename std::__remove_cvref_t<_ExecPolicy>>::value,
>
> The typename before std::__remove_cvref_t shouldn't be there.
>
>>+                            _T>::type;
>>+#else
>> using __enable_if_execution_policy =
>>     typename std::enable_if<__pstl::execution::is_execution_policy<typename std::decay<_ExecPolicy>::type>::value,
>>                             _T>::type;
>>+#endif
>> } // namespace __internal
>>
>> } // namespace __pstl
>> -- 
>>2.20.1
>>