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LWG 3039 Unnecessary decay in thread and packaged_task 

* include/std/future (__constrain_pkgdtask): Replace with ...
	(packaged_task::__not_same): New alias template, using
	__remove_cvref_t instead of decay.
	* include/std/thread (thread::__not_same): Add comment.

From-SVN: r261618
This commit is contained in:
Jonathan Wakely 2018-06-15 01:19:07 +01:00 committed by Jonathan Wakely
parent 024e96b90b
commit cb4f9a8c05
3 changed files with 18 additions and 14 deletions
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8
libstdc++-v3/ChangeLog
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@ -1,3 +1,11 @@
2018-06-15 Jonathan Wakely <jwakely@redhat.com>
LWG 3039 Unnecessary decay in thread and packaged_task
* include/std/future (__constrain_pkgdtask): Replace with ...
(packaged_task::__not_same): New alias template, using
__remove_cvref_t instead of decay.
* include/std/thread (thread::__not_same): Add comment.
2018-06-14 Jonathan Wakely <jwakely@redhat.com>
LWG 3075 basic_string needs deduction guides from basic_string_view

23
libstdc++-v3/include/std/future
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@ -1462,15 +1462,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
static_cast<_Alloc&>(_M_impl));
}
template<typename _Task, typename _Fn, bool
= is_same<_Task, typename decay<_Fn>::type>::value>
struct __constrain_pkgdtask
{ typedef void __type; };
template<typename _Task, typename _Fn>
struct __constrain_pkgdtask<_Task, _Fn, true>
{ };
/// packaged_task
template<typename _Res, typename... _ArgTypes>
class packaged_task<_Res(_ArgTypes...)>
@ -1478,6 +1469,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
typedef __future_base::_Task_state_base<_Res(_ArgTypes...)> _State_type;
shared_ptr<_State_type> _M_state;
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3039. Unnecessary decay in thread and packaged_task
template<typename _Fn, typename _Fn2 = __remove_cvref_t<_Fn>>
using __not_same
= typename enable_if<!is_same<packaged_task, _Fn2>::value>::type;
public:
// Construction and destruction
packaged_task() noexcept { }
@ -1488,8 +1485,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
packaged_task(allocator_arg_t, const _Allocator& __a) noexcept
{ }
template<typename _Fn, typename = typename
__constrain_pkgdtask<packaged_task, _Fn>::__type>
template<typename _Fn, typename = __not_same<_Fn>>
explicit
packaged_task(_Fn&& __fn)
: packaged_task(allocator_arg, std::allocator<int>(),
@ -1499,11 +1495,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 2097. packaged_task constructors should be constrained
// 2407. [this constructor should not be] explicit
template<typename _Fn, typename _Alloc, typename = typename
__constrain_pkgdtask<packaged_task, _Fn>::__type>
template<typename _Fn, typename _Alloc, typename = __not_same<_Fn>>
packaged_task(allocator_arg_t, const _Alloc& __a, _Fn&& __fn)
: _M_state(__create_task_state<_Res(_ArgTypes...)>(
std::forward<_Fn>(__fn), __a))
std::forward<_Fn>(__fn), __a))
{ }
~packaged_task()

1
libstdc++-v3/include/std/thread
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@ -104,6 +104,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 2097. packaged_task constructors should be constrained
// 3039. Unnecessary decay in thread and packaged_task
template<typename _Tp>
using __not_same = __not_<is_same<__remove_cvref_t<_Tp>, thread>>;