libcxx/test/std/containers/sequences/array/array.special/swap.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 // <array>
  10
  11 // template <class T, size_t N> void swap(array<T,N>& x, array<T,N>& y);
  12
  13 #include <array>
  14 #include <cassert>
  15
  16 #include "test_macros.h"
  17 // std::array is explicitly allowed to be initialized with A a = { init-list };.
  18 // Disable the missing braces warning for this reason.
  19 #include "disable_missing_braces_warning.h"
  20
  21 struct NonSwappable {
  22   NonSwappable() {}
  23 private:
  24   NonSwappable(NonSwappable const&);
  25   NonSwappable& operator=(NonSwappable const&);
  26 };
  27
  28 template <class Tp>
  29 decltype(swap(std::declval<Tp>(), std::declval<Tp>()))
  30 can_swap_imp(int);
  31
  32 template <class Tp>
  33 std::false_type can_swap_imp(...);
  34
  35 template <class Tp>
  36 struct can_swap : std::is_same<decltype(can_swap_imp<Tp>(0)), void> {};
  37
  38 int main(int, char**)
  39 {
  40     {
  41         typedef double T;
  42         typedef std::array<T, 3> C;
  43         C c1 = {1, 2, 3.5};
  44         C c2 = {4, 5, 6.5};
  45         swap(c1, c2);
  46         assert(c1.size() == 3);
  47         assert(c1[0] == 4);
  48         assert(c1[1] == 5);
  49         assert(c1[2] == 6.5);
  50         assert(c2.size() == 3);
  51         assert(c2[0] == 1);
  52         assert(c2[1] == 2);
  53         assert(c2[2] == 3.5);
  54     }
  55     {
  56         typedef double T;
  57         typedef std::array<T, 0> C;
  58         C c1 = {};
  59         C c2 = {};
  60         swap(c1, c2);
  61         assert(c1.size() == 0);
  62         assert(c2.size() == 0);
  63     }
  64     {
  65         typedef NonSwappable T;
  66         typedef std::array<T, 0> C0;
  67         static_assert(can_swap<C0&>::value, "");
  68         C0 l = {};
  69         C0 r = {};
  70         swap(l, r);
  71 #if TEST_STD_VER >= 11
  72         static_assert(noexcept(swap(l, r)), "");
  73 #endif
  74     }
  75 #if TEST_STD_VER >= 11
  76     {
  77         // NonSwappable is still considered swappable in C++03 because there
  78         // is no access control SFINAE.
  79         typedef NonSwappable T;
  80         typedef std::array<T, 42> C1;
  81         static_assert(!can_swap<C1&>::value, "");
  82     }
  83 #endif
  84
  85   return 0;
  86 }