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 T> struct variant_size; // undefined
14// template <class T> struct variant_size<const T>;
15// template <class T> struct variant_size<volatile T>;
16// template <class T> struct variant_size<const volatile T>;
17// template <class T> constexpr size_t variant_size_v
18// = variant_size<T>::value;
19
20#include <memory>
21#include <type_traits>
22#include <variant>
23
24#include "test_macros.h"
25
26template <class V, std::size_t E> void test() {
27 static_assert(std::variant_size<V>::value == E, "");
28 static_assert(std::variant_size<const V>::value == E, "");
29 static_assert(std::variant_size<volatile V>::value == E, "");
30 static_assert(std::variant_size<const volatile V>::value == E, "");
31 static_assert(std::variant_size_v<V> == E, "");
32 static_assert(std::variant_size_v<const V> == E, "");
33 static_assert(std::variant_size_v<volatile V> == E, "");
34 static_assert(std::variant_size_v<const volatile V> == E, "");
35 static_assert(std::is_base_of<std::integral_constant<std::size_t, E>,
36 std::variant_size<V>>::value,
37 "");
38};
39
40int main(int, char**) {
41 test<std::variant<>, 0>();
42 test<std::variant<void *>, 1>();
43 test<std::variant<long, long, void *, double>, 4>();
44
45 return 0;
46}
47

source code of libcxx/test/std/utilities/variant/variant.helpers/variant_size.pass.cpp