test/libcxx/utilities/optional/optional.object/triviality.abi.pass.cpp

//===----------------------------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++98, c++03, c++11, c++14

// <optional>

// This test asserts the triviality of special member functions of optional<T>
// whenever T has these special member functions trivial. The goal of this test
// is to make sure that we do not change the triviality of those, since that
// constitues an ABI break (small enough optionals would be passed by registers).
//
// constexpr optional(const optional& rhs);
// constexpr optional(optional&& rhs) noexcept(see below);
// constexpr optional<T>& operator=(const optional& rhs);
// constexpr optional<T>& operator=(optional&& rhs) noexcept(see below);

#include <optional>
#include <type_traits>
#include <cassert>

#include "archetypes.hpp"

template <class T>
struct SpecialMemberTest {
    using O = std::optional<T>;

    static_assert(std::is_trivially_destructible_v<O> ==
        std::is_trivially_destructible_v<T>,
        "optional<T> is trivially destructible if and only if T is.");

    static_assert(std::is_trivially_copy_constructible_v<O> ==
        std::is_trivially_copy_constructible_v<T>,
        "optional<T> is trivially copy constructible if and only if T is.");

    static_assert(std::is_trivially_move_constructible_v<O> ==
        std::is_trivially_move_constructible_v<T> ||
        (!std::is_move_constructible_v<T> && std::is_trivially_copy_constructible_v<T>),
        "optional<T> is trivially move constructible if T is trivially move constructible, "
        "or if T is trivially copy constructible and is not move constructible.");

    static_assert(std::is_trivially_copy_assignable_v<O> ==
        (std::is_trivially_destructible_v<T> &&
         std::is_trivially_copy_constructible_v<T> &&
         std::is_trivially_copy_assignable_v<T>),
        "optional<T> is trivially copy assignable if and only if T is trivially destructible, "
        "trivially copy constructible, and trivially copy assignable.");

    static_assert(std::is_trivially_move_assignable_v<O> ==
        (std::is_trivially_destructible_v<T> &&
         ((std::is_trivially_move_constructible_v<T> && std::is_trivially_move_assignable_v<T>) ||
          ((!std::is_move_constructible_v<T> || !std::is_move_assignable_v<T>) &&
           std::is_trivially_copy_constructible_v<T> && std::is_trivially_copy_assignable_v<T>))),
        "optional<T> is trivially move assignable if T is trivially destructible, and either "
        "(1) trivially move constructible and trivially move assignable, or "
        "(2) not move constructible or not move assignable, and "
        "trivially copy constructible and trivially copy assignable.");
};

template <class ...Args> static void sink(Args&&...) {}

template <class ...TestTypes>
struct DoTestsMetafunction {
    DoTestsMetafunction() { sink(SpecialMemberTest<TestTypes>{}...); }
};

struct TrivialMoveNonTrivialCopy {
    TrivialMoveNonTrivialCopy() = default;
    TrivialMoveNonTrivialCopy(const TrivialMoveNonTrivialCopy&) {}
    TrivialMoveNonTrivialCopy(TrivialMoveNonTrivialCopy&&) = default;
    TrivialMoveNonTrivialCopy& operator=(const TrivialMoveNonTrivialCopy&) { return *this; }
    TrivialMoveNonTrivialCopy& operator=(TrivialMoveNonTrivialCopy&&) = default;
};

struct TrivialCopyNonTrivialMove {
    TrivialCopyNonTrivialMove() = default;
    TrivialCopyNonTrivialMove(const TrivialCopyNonTrivialMove&) = default;
    TrivialCopyNonTrivialMove(TrivialCopyNonTrivialMove&&) {}
    TrivialCopyNonTrivialMove& operator=(const TrivialCopyNonTrivialMove&) = default;
    TrivialCopyNonTrivialMove& operator=(TrivialCopyNonTrivialMove&&) { return *this; }
};

int main()
{
    sink(
        ImplicitTypes::ApplyTypes<DoTestsMetafunction>{},
        ExplicitTypes::ApplyTypes<DoTestsMetafunction>{},
        NonLiteralTypes::ApplyTypes<DoTestsMetafunction>{},
        NonTrivialTypes::ApplyTypes<DoTestsMetafunction>{},
        DoTestsMetafunction<TrivialMoveNonTrivialCopy, TrivialCopyNonTrivialMove>{}
    );
}