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, c++11, c++14
10
11// <variant>
12
13// template <class ...Types> class variant;
14
15// constexpr variant() noexcept(see below);
16
17#include <cassert>
18#include <type_traits>
19#include <variant>
20#include <string>
21
22#include "test_macros.h"
23#include "variant_test_helpers.h"
24
25struct NonDefaultConstructible {
26 constexpr NonDefaultConstructible(int) {}
27};
28
29struct NotNoexcept {
30 NotNoexcept() noexcept(false) {}
31};
32
33#ifndef TEST_HAS_NO_EXCEPTIONS
34struct DefaultCtorThrows {
35 DefaultCtorThrows() { throw 42; }
36};
37#endif
38
39constexpr void test_default_ctor_sfinae() {
40 {
41 using V = std::variant<std::monostate, int>;
42 static_assert(std::is_default_constructible<V>::value, "");
43 }
44 {
45 using V = std::variant<NonDefaultConstructible, int>;
46 static_assert(!std::is_default_constructible<V>::value, "");
47 }
48}
49
50constexpr void test_default_ctor_noexcept() {
51 {
52 using V = std::variant<int>;
53 static_assert(std::is_nothrow_default_constructible<V>::value, "");
54 }
55 {
56 using V = std::variant<NotNoexcept>;
57 static_assert(!std::is_nothrow_default_constructible<V>::value, "");
58 }
59}
60
61void test_default_ctor_throws() {
62#ifndef TEST_HAS_NO_EXCEPTIONS
63 using V = std::variant<DefaultCtorThrows, int>;
64 try {
65 V v;
66 assert(false);
67 } catch (const int& ex) {
68 assert(ex == 42);
69 } catch (...) {
70 assert(false);
71 }
72#endif
73}
74
75constexpr void test_default_ctor_basic() {
76 {
77 std::variant<int> v;
78 assert(v.index() == 0);
79 assert(std::get<0>(v) == 0);
80 }
81 {
82 std::variant<int, long> v;
83 assert(v.index() == 0);
84 assert(std::get<0>(v) == 0);
85 }
86 {
87 std::variant<int, NonDefaultConstructible> v;
88 assert(v.index() == 0);
89 assert(std::get<0>(v) == 0);
90 }
91 {
92 using V = std::variant<int, long>;
93 constexpr V v;
94 static_assert(v.index() == 0, "");
95 static_assert(std::get<0>(v: v) == 0, "");
96 }
97 {
98 using V = std::variant<int, long>;
99 constexpr V v;
100 static_assert(v.index() == 0, "");
101 static_assert(std::get<0>(v: v) == 0, "");
102 }
103 {
104 using V = std::variant<int, NonDefaultConstructible>;
105 constexpr V v;
106 static_assert(v.index() == 0, "");
107 static_assert(std::get<0>(v: v) == 0, "");
108 }
109}
110
111constexpr void issue_86686() {
112#if TEST_STD_VER >= 20
113 static_assert(std::variant<std::string>{}.index() == 0);
114#endif
115}
116
117constexpr bool test() {
118 test_default_ctor_basic();
119 test_default_ctor_sfinae();
120 test_default_ctor_noexcept();
121 issue_86686();
122
123 return true;
124}
125
126int main(int, char**) {
127 test();
128 test_default_ctor_throws();
129 static_assert(test());
130 return 0;
131}
132

source code of libcxx/test/std/utilities/variant/variant.variant/variant.ctor/default.pass.cpp