libcxx/test/std/utilities/variant/variant.helpers/variant_size.pass.cpp

   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
  26 template <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
  40 int 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 }