1 //===----------------------------------------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 // <functional>
11 
12 // placeholders
13 // The placeholders are constexpr in C++17 and beyond.
14 // libc++ provides constexpr placeholders in C++11 and beyond.
15 
16 #include <functional>
17 #include <type_traits>
18 
19 #include "test_macros.h"
20 
21 template <class T>
22 void
test(const T & t)23 test(const T& t)
24 {
25     // Test default constructible.
26     T t2;
27     ((void)t2);
28     // Test copy constructible.
29     T t3 = t;
30     ((void)t3);
31     static_assert(std::is_nothrow_copy_constructible<T>::value, "");
32     static_assert(std::is_nothrow_move_constructible<T>::value, "");
33 }
34 
35 #if TEST_STD_VER >= 11
36 constexpr decltype(std::placeholders::_1)  default1{};
37 constexpr decltype(std::placeholders::_2)  default2{};
38 constexpr decltype(std::placeholders::_3)  default3{};
39 constexpr decltype(std::placeholders::_4)  default4{};
40 constexpr decltype(std::placeholders::_5)  default5{};
41 constexpr decltype(std::placeholders::_6)  default6{};
42 constexpr decltype(std::placeholders::_7)  default7{};
43 constexpr decltype(std::placeholders::_8)  default8{};
44 constexpr decltype(std::placeholders::_9)  default9{};
45 constexpr decltype(std::placeholders::_10) default10{};
46 
47 constexpr decltype(std::placeholders::_1)  cp1 = std::placeholders::_1;
48 constexpr decltype(std::placeholders::_2)  cp2 = std::placeholders::_2;
49 constexpr decltype(std::placeholders::_3)  cp3 = std::placeholders::_3;
50 constexpr decltype(std::placeholders::_4)  cp4 = std::placeholders::_4;
51 constexpr decltype(std::placeholders::_5)  cp5 = std::placeholders::_5;
52 constexpr decltype(std::placeholders::_6)  cp6 = std::placeholders::_6;
53 constexpr decltype(std::placeholders::_7)  cp7 = std::placeholders::_7;
54 constexpr decltype(std::placeholders::_8)  cp8 = std::placeholders::_8;
55 constexpr decltype(std::placeholders::_9)  cp9 = std::placeholders::_9;
56 constexpr decltype(std::placeholders::_10) cp10 = std::placeholders::_10;
57 #endif // TEST_STD_VER >= 11
58 
use_placeholders_to_prevent_unused_warning()59 void use_placeholders_to_prevent_unused_warning() {
60 #if TEST_STD_VER >= 11
61   ((void)cp1);
62   ((void)cp2);
63   ((void)cp3);
64   ((void)cp4);
65   ((void)cp5);
66   ((void)cp6);
67   ((void)cp7);
68   ((void)cp8);
69   ((void)cp9);
70   ((void)cp10);
71   ((void)default1);
72   ((void)default2);
73   ((void)default3);
74   ((void)default4);
75   ((void)default5);
76   ((void)default6);
77   ((void)default7);
78   ((void)default8);
79   ((void)default9);
80   ((void)default10);
81 #endif
82 }
83 
main()84 int main()
85 {
86     use_placeholders_to_prevent_unused_warning();
87     test(std::placeholders::_1);
88     test(std::placeholders::_2);
89     test(std::placeholders::_3);
90     test(std::placeholders::_4);
91     test(std::placeholders::_5);
92     test(std::placeholders::_6);
93     test(std::placeholders::_7);
94     test(std::placeholders::_8);
95     test(std::placeholders::_9);
96     test(std::placeholders::_10);
97 }
98