LWG 3039 changed the spec to use remove_cvref_t instead of decay_t,
and this patch makes that change to our std::packaged_task. I'm not
sure why I created a custom type at namespace scope to constrain
packaged_task. This patch replaces it with an alias for enable_if.
std::thread already had the change, so this just adds a comment noting
the issue number.
* 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.
Tested powerpc64le-linux, committed to trunk.
commit df8c05879aa008a993cbd5f0762f9ef8557f2bb7
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Thu Jun 14 23:36:09 2018 +0100
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.
diff --git a/libstdc++-v3/include/std/future b/libstdc++-v3/include/std/future
index c17a253d26e..937c05ef2b2 100644
--- a/libstdc++-v3/include/std/future
+++ b/libstdc++-v3/include/std/future
@@ -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()
diff --git a/libstdc++-v3/include/std/thread b/libstdc++-v3/include/std/thread
index 61861b58520..13acd6a3091 100644
--- a/libstdc++-v3/include/std/thread
+++ b/libstdc++-v3/include/std/thread
@@ -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>>;
