106 lines · cpp
1//===----------------------------------------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9// UNSUPPORTED: c++03, c++11, c++14, c++17, c++2010 11// template<class... Args>12// constexpr T& emplace(Args&&... args) noexcept;13// Constraints: is_nothrow_constructible_v<T, Args...> is true.14//15// Effects: Equivalent to:16// if (has_value()) {17// destroy_at(addressof(val));18// } else {19// destroy_at(addressof(unex));20// has_val = true;21// }22// return *construct_at(addressof(val), std::forward<Args>(args)...);23 24#include <cassert>25#include <concepts>26#include <expected>27#include <type_traits>28#include <utility>29 30#include "../../types.h"31#include "test_macros.h"32 33template <class T, class... Args>34concept CanEmplace = requires(T t, Args&&... args) { t.emplace(std::forward<Args>(args)...); };35 36static_assert(CanEmplace<std::expected<int, int>, int>);37 38template <bool Noexcept>39struct CtorFromInt {40 CtorFromInt(int) noexcept(Noexcept);41 CtorFromInt(int, int) noexcept(Noexcept);42};43 44static_assert(CanEmplace<std::expected<CtorFromInt<true>, int>, int>);45static_assert(CanEmplace<std::expected<CtorFromInt<true>, int>, int, int>);46static_assert(!CanEmplace<std::expected<CtorFromInt<false>, int>, int>);47static_assert(!CanEmplace<std::expected<CtorFromInt<false>, int>, int, int>);48 49constexpr bool test() {50 // has_value51 {52 BothNoexcept::state oldState{};53 BothNoexcept::state newState{};54 std::expected<BothNoexcept, int> e(std::in_place, oldState, 5);55 decltype(auto) x = e.emplace(newState, 10);56 static_assert(std::same_as<decltype(x), BothNoexcept&>);57 assert(&x == &(*e));58 59 assert(oldState.dtorCalled);60 assert(e.has_value());61 assert(e.value().data_ == 10);62 }63 64 // !has_value65 {66 BothMayThrow::state oldState{};67 std::expected<int, BothMayThrow> e(std::unexpect, oldState, 5);68 decltype(auto) x = e.emplace(10);69 static_assert(std::same_as<decltype(x), int&>);70 assert(&x == &(*e));71 72 assert(oldState.dtorCalled);73 assert(e.has_value());74 assert(e.value() == 10);75 }76 77 // TailClobberer78 {79 std::expected<TailClobberer<0>, bool> e(std::unexpect);80 e.emplace();81 assert(e.has_value());82 }83 84 // CheckForInvalidWrites85 {86 {87 CheckForInvalidWrites<true> e;88 e.emplace();89 assert(e.check());90 }91 {92 CheckForInvalidWrites<false> e;93 e.emplace();94 assert(e.check());95 }96 }97 98 return true;99}100 101int main(int, char**) {102 test();103 static_assert(test());104 return 0;105}106