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// test forward
12
13#include <utility>
14#include <type_traits>
15#include <cassert>
16
17#include "test_macros.h"
18
19struct A
20{
21};
22
23A source() TEST_NOEXCEPT {return A();}
24const A csource() TEST_NOEXCEPT {return A();}
25
26
27#if TEST_STD_VER > 11
28constexpr bool test_constexpr_forward() {
29 int x = 42;
30 const int cx = 101;
31 return std::forward<int&>(x) == 42
32 && std::forward<int>(x) == 42
33 && std::forward<const int&>(x) == 42
34 && std::forward<const int>(x) == 42
35 && std::forward<int&&>(x) == 42
36 && std::forward<const int&&>(x) == 42
37 && std::forward<const int&>(cx) == 101
38 && std::forward<const int>(cx) == 101;
39}
40#endif
41
42int main(int, char**)
43{
44 A a;
45 const A ca = A();
46
47 ((void)a); // Prevent unused warning
48 ((void)ca); // Prevent unused warning
49
50 static_assert(std::is_same<decltype(std::forward<A&>(a)), A&>::value, "");
51 static_assert(std::is_same<decltype(std::forward<A>(a)), A&&>::value, "");
52 static_assert(std::is_same<decltype(std::forward<A>(source())), A&&>::value, "");
53 ASSERT_NOEXCEPT(std::forward<A&>(a));
54 ASSERT_NOEXCEPT(std::forward<A>(a));
55 ASSERT_NOEXCEPT(std::forward<A>(source()));
56
57 static_assert(std::is_same<decltype(std::forward<const A&>(a)), const A&>::value, "");
58 static_assert(std::is_same<decltype(std::forward<const A>(a)), const A&&>::value, "");
59 static_assert(std::is_same<decltype(std::forward<const A>(source())), const A&&>::value, "");
60 ASSERT_NOEXCEPT(std::forward<const A&>(a));
61 ASSERT_NOEXCEPT(std::forward<const A>(a));
62 ASSERT_NOEXCEPT(std::forward<const A>(source()));
63
64 static_assert(std::is_same<decltype(std::forward<const A&>(ca)), const A&>::value, "");
65 static_assert(std::is_same<decltype(std::forward<const A>(ca)), const A&&>::value, "");
66 static_assert(std::is_same<decltype(std::forward<const A>(csource())), const A&&>::value, "");
67 ASSERT_NOEXCEPT(std::forward<const A&>(ca));
68 ASSERT_NOEXCEPT(std::forward<const A>(ca));
69 ASSERT_NOEXCEPT(std::forward<const A>(csource()));
70
71#if TEST_STD_VER > 11
72 {
73 constexpr int i2 = std::forward<int>(42);
74 static_assert(std::forward<int>(42) == 42, "");
75 static_assert(std::forward<const int&>(i2) == 42, "");
76 static_assert(test_constexpr_forward(), "");
77 }
78#endif
79#if TEST_STD_VER == 11 && defined(_LIBCPP_VERSION)
80 // Test that std::forward is constexpr in C++11. This is an extension
81 // provided by both libc++ and libstdc++.
82 {
83 constexpr int i2 = std::forward<int>(42);
84 static_assert(std::forward<int>(42) == 42, "" );
85 static_assert(std::forward<const int&>(i2) == 42, "");
86 }
87#endif
88
89 return 0;
90}
91

source code of libcxx/test/std/utilities/utility/forward/forward.pass.cpp