[libcxx-commits] [libcxx] [libc++] Implement P1901R2: owner_hash and owner_equal for shared_ptr/weak_ptr (PR #210551)

[Hristo Hristov via libcxx-commits]

================
@@ -0,0 +1,40 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14, c++17, c++20, c++23
+
+// <memory>
+
+// shared_ptr
+
+// template<class U> bool owner_equal(shared_ptr<U> const& b) const noexcept;
+
+#include <memory>
+#include <cassert>
+#include "test_macros.h"
+
+int main(int, char**) {
+  const std::shared_ptr<int> p1(new int);
+  const std::shared_ptr<int> p2 = p1;
+  const std::shared_ptr<int> p3(new int);
+  const std::shared_ptr<void> empty1;
+  const std::shared_ptr<long> empty2;
+
+  assert(p1.owner_equal(p2));
+  assert(p2.owner_equal(p1));
+  assert(!p1.owner_equal(p3));
+  assert(!p3.owner_equal(p1));
+
+  assert(empty1.owner_equal(empty2));
+  assert(!p1.owner_equal(empty1));
+
+  ASSERT_SAME_TYPE(decltype(p1.owner_equal(p2)), bool);
+  ASSERT_NOEXCEPT(p1.owner_equal(p2));
----------------
Zingam wrote:

Nit: The above is correct but in newer test when possible we prefer to use the non-macro versions. For example the following patterns:

```suggestion
  std::same_as<bool> decltype(auto) result = p1.owner(p2);
  assert(result));
  static_assert(noexcept(p1.owner_equal(p2)));
  
  ...etc...
```

There is no specific order required but you can order them for easier reading.

https://github.com/llvm/llvm-project/pull/210551