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libstdc++: Use type_identity_t for non-deducible std::atomic_xxx args

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This is LWG 3220 which is about to become Tentatively Ready.

libstdc++-v3/ChangeLog:

	* include/std/atomic (__atomic_val_t): Use __type_identity_t
	instead of atomic<T>::value_type, as per LWG 3220.
	* testsuite/29_atomics/atomic/lwg3220.cc: New test.
This commit is contained in:
Jonathan Wakely 2022-06-13 16:36:14 +01:00
parent b3dd7d8b48
commit 30cc1b65e4
2 changed files with 16 additions and 1 deletions
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4
libstdc++-v3/include/std/atomic
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@ -1244,8 +1244,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
{ atomic_flag_clear_explicit(__a, memory_order_seq_cst); }
/// @cond undocumented
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 3220. P0558 broke conforming C++14 uses of atomic shared_ptr
template<typename _Tp>
using __atomic_val_t = typename atomic<_Tp>::value_type;
using __atomic_val_t = __type_identity_t<_Tp>;
template<typename _Tp>
using __atomic_diff_t = typename atomic<_Tp>::difference_type;
/// @endcond

13
libstdc++-v3/testsuite/29_atomics/atomic/lwg3220.cc Normal file
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@ -0,0 +1,13 @@
// { dg-do compile { target c++11 } }
// DR 3220. P0558 broke conforming C++14 uses of atomic shared_ptr
#include <atomic>
#include <memory>
struct Abstract { virtual void test() = 0; };
struct Concrete : Abstract { virtual void test() override {} };
int main() {
std::shared_ptr<Abstract> ptr;
std::atomic_store<Abstract>(&ptr, std::make_shared<Concrete>());
}