[libcxx-commits] [libcxx] [libc++] Make std::pair trivially copyable if its members are (PR #89652)

[via libcxx-commits]

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@@ -0,0 +1,95 @@
+//===----------------------------------------------------------------------===//
+//
+// 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: gcc && (c++11 || c++14 || c++17)
+
+#include <type_traits>
+#include <utility>
+
+#include "test_macros.h"
+
+struct trivially_copyable {
+  int arr[4];
+};
+
+struct trivially_copyable_no_assignment {
+  int arr[4];
+  trivially_copyable_no_assignment& operator=(const trivially_copyable_no_assignment&) = delete;
+};
+static_assert(std::is_trivially_copyable<trivially_copyable_no_assignment>::value, "");
+
+static_assert(std::is_trivially_copy_constructible<std::pair<trivially_copyable_no_assignment, int> >::value, "");
+static_assert(std::is_trivially_move_constructible<std::pair<trivially_copyable_no_assignment, int> >::value, "");
+#if TEST_STD_VER >= 11 // This is https://llvm.org/PR90605
+static_assert(!std::is_trivially_copy_assignable<std::pair<trivially_copyable_no_assignment, int> >::value, "");
+static_assert(!std::is_trivially_move_assignable<std::pair<trivially_copyable_no_assignment, int> >::value, "");
+#endif // TEST_STD_VER >= 11
+static_assert(std::is_trivially_destructible<std::pair<trivially_copyable_no_assignment, int> >::value, "");
+
+struct trivially_copyable_no_construction {
+  int arr[4];
+  trivially_copyable_no_construction()                                                     = default;
+  trivially_copyable_no_construction(const trivially_copyable_no_construction&)            = delete;
+  trivially_copyable_no_construction& operator=(const trivially_copyable_no_construction&) = default;
+};
+static_assert(std::is_trivially_copyable<trivially_copyable_no_construction>::value, "");
+
+#ifdef _LIBCPP_ABI_TRIVIALLY_COPYABLE_PAIR
+static_assert(!std::is_trivially_copy_constructible<std::pair<trivially_copyable_no_construction, int> >::value, "");
+static_assert(!std::is_trivially_move_constructible<std::pair<trivially_copyable_no_construction, int> >::value, "");
+static_assert(std::is_trivially_copy_assignable<std::pair<trivially_copyable_no_construction, int> >::value, "");
+static_assert(std::is_trivially_move_assignable<std::pair<trivially_copyable_no_construction, int> >::value, "");
+static_assert(std::is_trivially_destructible<std::pair<trivially_copyable_no_construction, int> >::value, "");
+#else // _LIBCPP_ABI_TRIVIALLY_COPYABLE_PAIR
+#  if TEST_STD_VER >= 11
+static_assert(!std::is_trivially_copy_constructible<std::pair<trivially_copyable_no_construction, int> >::value, "");
+static_assert(!std::is_trivially_move_constructible<std::pair<trivially_copyable_no_construction, int> >::value, "");
+#  endif // TEST_STD_VER >= 11
+static_assert(!std::is_trivially_copy_assignable<std::pair<trivially_copyable_no_construction, int> >::value, "");
+static_assert(!std::is_trivially_move_assignable<std::pair<trivially_copyable_no_construction, int> >::value, "");
+static_assert(std::is_trivially_destructible<std::pair<trivially_copyable_no_construction, int> >::value, "");
+#endif   // _LIBCPP_ABI_TRIVIALLY_COPYABLE_PAIR
+
+static_assert(!std::is_trivially_copyable<std::pair<int&, int> >::value, "");
+static_assert(!std::is_trivially_copyable<std::pair<int, int&> >::value, "");
+static_assert(!std::is_trivially_copyable<std::pair<int&, int&> >::value, "");
+
+#ifdef _LIBCPP_ABI_TRIVIALLY_COPYABLE_PAIR
+static_assert(std::is_trivially_copyable<std::pair<int, int> >::value, "");
+static_assert(std::is_trivially_copyable<std::pair<int, char> >::value, "");
+static_assert(std::is_trivially_copyable<std::pair<char, int> >::value, "");
+static_assert(std::is_trivially_copyable<std::pair<std::pair<char, char>, int> >::value, "");
+static_assert(std::is_trivially_copyable<std::pair<trivially_copyable, int> >::value, "");
+static_assert(std::is_trivially_copyable<std::pair<trivially_copyable_no_assignment, int> >::value, "");
+static_assert(std::is_trivially_copyable<std::pair<trivially_copyable_no_construction, int> >::value, "");
+
+static_assert(std::is_trivially_copy_constructible<std::pair<int, int> >::value, "");
+static_assert(std::is_trivially_move_constructible<std::pair<int, int> >::value, "");
+static_assert(std::is_trivially_copy_assignable<std::pair<int, int> >::value, "");
+static_assert(std::is_trivially_move_assignable<std::pair<int, int> >::value, "");
+static_assert(std::is_trivially_destructible<std::pair<int, int> >::value, "");
+
+#else                      // _LIBCPP_ABI_TRIVIALLY_COPYABLE_PAIR
+static_assert(!std::is_trivially_copyable<std::pair<int, int> >::value, "");
+static_assert(!std::is_trivially_copyable<std::pair<int, char> >::value, "");
+static_assert(!std::is_trivially_copyable<std::pair<char, int> >::value, "");
+static_assert(!std::is_trivially_copyable<std::pair<std::pair<char, char>, int> >::value, "");
+static_assert(!std::is_trivially_copyable<std::pair<trivially_copyable, int> >::value, "");
+#  if TEST_STD_VER >= 23
+static_assert(!std::is_trivially_copyable<std::pair<trivially_copyable_no_assignment, int> >::value, "");
----------------
EricWF wrote:

OK, so this is less of a problem than I initially thought.

`is_trivially_copyable` affects a few things in the library, some of which are still potentially breakages. But it doesn't, in this case, actually reflect a change in the x86 calling conventions, since the affected members that changed the triviality are the assignment operators.

https://github.com/llvm/llvm-project/pull/89652