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-exception
6//
7//===----------------------------------------------------------------------===//
8
9// UNSUPPORTED: c++03
10
11// <queue>
12
13// template <class... Args> decltype(auto) emplace(Args&&... args);
14// return type is 'decltype(auto)' in C++17; 'void' before
15// whatever the return type of the underlying container's emplace_back() returns.
16
17#include <queue>
18#include <cassert>
19#include <list>
20
21#include "test_macros.h"
22
23#include "../../../Emplaceable.h"
24
25template <typename Queue>
26void test_return_type() {
27 typedef typename Queue::container_type Container;
28 typedef typename Container::value_type value_type;
29 typedef decltype(std::declval<Queue>().emplace(std::declval<value_type&>())) queue_return_type;
30
31#if TEST_STD_VER > 14
32 typedef decltype(std::declval<Container>().emplace_back(std::declval<value_type>())) container_return_type;
33 static_assert(std::is_same<queue_return_type, container_return_type>::value, "");
34#else
35 static_assert(std::is_same<queue_return_type, void>::value, "");
36#endif
37}
38
39int main(int, char**) {
40 test_return_type<std::queue<int> >();
41 test_return_type<std::queue<int, std::list<int> > >();
42
43 std::queue<Emplaceable> q;
44#if TEST_STD_VER > 14
45 typedef Emplaceable T;
46 T& r1 = q.emplace(1, 2.5);
47 assert(&r1 == &q.back());
48 T& r2 = q.emplace(2, 3.5);
49 assert(&r2 == &q.back());
50 T& r3 = q.emplace(3, 4.5);
51 assert(&r3 == &q.back());
52 assert(&r1 == &q.front());
53#else
54 q.emplace(1, 2.5);
55 q.emplace(2, 3.5);
56 q.emplace(3, 4.5);
57#endif
58
59 assert(q.size() == 3);
60 assert(q.front() == Emplaceable(1, 2.5));
61 assert(q.back() == Emplaceable(3, 4.5));
62
63 return 0;
64}
65

source code of libcxx/test/std/containers/container.adaptors/queue/queue.defn/emplace.pass.cpp