[libc++] Fix bug in **tests** for std::atomic_ref<T*> increment and decrement operators

[dalg24]

Fix https://github.com/llvm/llvm-project/pull/121414/files#r1908697882

The implementation is fine and has the proper increment/decrement operators defined

llvm-project/libcxx/include/__atomic/atomic_ref.h

Lines 364 to 367 in b4e17d4

	_LIBCPP_HIDE_FROM_ABI _Tp* operator++(int) const noexcept { return fetch_add(1); }
	_LIBCPP_HIDE_FROM_ABI _Tp* operator--(int) const noexcept { return fetch_sub(1); }
	_LIBCPP_HIDE_FROM_ABI _Tp* operator++() const noexcept { return fetch_add(1) + 1; }
	_LIBCPP_HIDE_FROM_ABI _Tp* operator--() const noexcept { return fetch_sub(1) - 1; }

The issue is in the tests

• a typo (T instead of std::atomic_ref<T>) when ensuring that increment/decrement operators are not defined in the primary template and specialization for floating point types, and
• the specialization for pointer types miscategorized.

[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Damien L-G (dalg24)

Changes

Fix https://github.com/llvm/llvm-project/pull/121414/files#r1908697882

The implementation is fine and has the proper increment/decrement operators defined

llvm-project/libcxx/include/__atomic/atomic_ref.h

Lines 364 to 367 in b4e17d4

	_LIBCPP_HIDE_FROM_ABI _Tp* operator++(int) const noexcept { return fetch_add(1); }
	_LIBCPP_HIDE_FROM_ABI _Tp* operator--(int) const noexcept { return fetch_sub(1); }
	_LIBCPP_HIDE_FROM_ABI _Tp* operator++() const noexcept { return fetch_add(1) + 1; }
	_LIBCPP_HIDE_FROM_ABI _Tp* operator--() const noexcept { return fetch_sub(1) - 1; }

The issue is in the tests

• a typo (T instead of std::atomic_ref<T>) when ensuring that increment/decrement operators are not defined in the primary template and specialization for floating point types, and
• the specialization for pointer types miscategorized.

---

Full diff: https://github.com/llvm/llvm-project/pull/122271.diff

1 Files Affected:

• (modified) libcxx/test/std/atomics/atomics.ref/increment_decrement.pass.cpp (+69-33)

diff --git a/libcxx/test/std/atomics/atomics.ref/increment_decrement.pass.cpp b/libcxx/test/std/atomics/atomics.ref/increment_decrement.pass.cpp
index f26a0bdf3663a5..0dfd797a908371 100644
--- a/libcxx/test/std/atomics/atomics.ref/increment_decrement.pass.cpp
+++ b/libcxx/test/std/atomics/atomics.ref/increment_decrement.pass.cpp
@@ -42,43 +42,79 @@ constexpr bool does_not_have_increment_nor_decrement_operators() {
 
 template <typename T>
 struct TestDoesNotHaveIncrementDecrement {
-  void operator()() const { static_assert(does_not_have_increment_nor_decrement_operators<T>()); }
+  void operator()() const { static_assert(does_not_have_increment_nor_decrement_operators<std::atomic_ref<T>>()); }
 };
 
 template <typename T>
 struct TestIncrementDecrement {
   void operator()() const {
-    static_assert(std::is_integral_v<T>);
-
-    T x(T(1));
-    std::atomic_ref<T> const a(x);
-
-    {
-      std::same_as<T> decltype(auto) y = ++a;
-      assert(y == T(2));
-      assert(x == T(2));
-      ASSERT_NOEXCEPT(++a);
-    }
-
-    {
-      std::same_as<T> decltype(auto) y = --a;
-      assert(y == T(1));
-      assert(x == T(1));
-      ASSERT_NOEXCEPT(--a);
-    }
-
-    {
-      std::same_as<T> decltype(auto) y = a++;
-      assert(y == T(1));
-      assert(x == T(2));
-      ASSERT_NOEXCEPT(a++);
-    }
-
-    {
-      std::same_as<T> decltype(auto) y = a--;
-      assert(y == T(2));
-      assert(x == T(1));
-      ASSERT_NOEXCEPT(a--);
+    static_assert(std::is_integral_v<T> || std::is_pointer_v<T>);
+    if constexpr (std::is_integral_v<T>) {
+      T x(T(1));
+      std::atomic_ref<T> const a(x);
+
+      {
+        std::same_as<T> decltype(auto) y = ++a;
+        assert(y == T(2));
+        assert(x == T(2));
+        ASSERT_NOEXCEPT(++a);
+      }
+
+      {
+        std::same_as<T> decltype(auto) y = --a;
+        assert(y == T(1));
+        assert(x == T(1));
+        ASSERT_NOEXCEPT(--a);
+      }
+
+      {
+        std::same_as<T> decltype(auto) y = a++;
+        assert(y == T(1));
+        assert(x == T(2));
+        ASSERT_NOEXCEPT(a++);
+      }
+
+      {
+        std::same_as<T> decltype(auto) y = a--;
+        assert(y == T(2));
+        assert(x == T(1));
+        ASSERT_NOEXCEPT(a--);
+      }
+    } else if constexpr (std::is_pointer_v<T>) {
+      using U = std::remove_pointer_t<T>;
+      U t[9]  = {};
+      T p{&t[1]};
+      std::atomic_ref<T> const a(p);
+
+      {
+        std::same_as<T> decltype(auto) y = ++a;
+        assert(y == &t[2]);
+        assert(p == &t[2]);
+        ASSERT_NOEXCEPT(++a);
+      }
+
+      {
+        std::same_as<T> decltype(auto) y = --a;
+        assert(y == &t[1]);
+        assert(p == &t[1]);
+        ASSERT_NOEXCEPT(--a);
+      }
+
+      {
+        std::same_as<T> decltype(auto) y = a++;
+        assert(y == &t[1]);
+        assert(p == &t[2]);
+        ASSERT_NOEXCEPT(a++);
+      }
+
+      {
+        std::same_as<T> decltype(auto) y = a--;
+        assert(y == &t[2]);
+        assert(p == &t[1]);
+        ASSERT_NOEXCEPT(a--);
+      }
+    } else {
+      static_assert(std::is_void_v<T>);
     }
   }
 };
@@ -88,7 +124,7 @@ int main(int, char**) {
 
   TestEachFloatingPointType<TestDoesNotHaveIncrementDecrement>()();
 
-  TestEachPointerType<TestDoesNotHaveIncrementDecrement>()();
+  TestEachPointerType<TestIncrementDecrement>()();
 
   TestDoesNotHaveIncrementDecrement<bool>()();
   TestDoesNotHaveIncrementDecrement<UserAtomicType>()();