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 18 #include <queue> 19 #include <cassert> 20 #include <list> 21 22 #include "test_macros.h" 23 24 #include "../../../Emplaceable.h" 25 26 template <typename Queue> 27 void test_return_type() { 28 typedef typename Queue::container_type Container; 29 typedef typename Container::value_type value_type; 30 typedef decltype(std::declval<Queue>().emplace(std::declval<value_type &>())) queue_return_type; 31 32 #if TEST_STD_VER > 14 33 typedef decltype(std::declval<Container>().emplace_back(std::declval<value_type>())) container_return_type; 34 static_assert(std::is_same<queue_return_type, container_return_type>::value, ""); 35 #else 36 static_assert(std::is_same<queue_return_type, void>::value, ""); 37 #endif 38 } 39 40 int main(int, char**) 41 { 42 test_return_type<std::queue<int> > (); 43 test_return_type<std::queue<int, std::list<int> > > (); 44 45 std::queue<Emplaceable> q; 46 #if TEST_STD_VER > 14 47 typedef Emplaceable T; 48 T& r1 = q.emplace(1, 2.5); 49 assert(&r1 == &q.back()); 50 T& r2 = q.emplace(2, 3.5); 51 assert(&r2 == &q.back()); 52 T& r3 = q.emplace(3, 4.5); 53 assert(&r3 == &q.back()); 54 assert(&r1 == &q.front()); 55 #else 56 q.emplace(1, 2.5); 57 q.emplace(2, 3.5); 58 q.emplace(3, 4.5); 59 #endif 60 61 assert(q.size() == 3); 62 assert(q.front() == Emplaceable(1, 2.5)); 63 assert(q.back() == Emplaceable(3, 4.5)); 64 65 return 0; 66 } 67