libcxx/test/std/strings/basic.string/string.cons/move_assign_noexcept.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
  10
  11 // <string>
  12
  13 // basic_string& operator=(basic_string&& c)
  14 //     noexcept(
  15 //         allocator_traits<allocator_type>::propagate_on_container_move_assignment::value ||
  16 //         allocator_traits<allocator_type>::is_always_equal::value); // C++17, constexpr since C++20
  17 //
  18 //  before C++17, we use the conforming extension
  19 //     noexcept(
  20 //         allocator_type::propagate_on_container_move_assignment::value &&
  21 //         is_nothrow_move_assignable<allocator_type>::value); // constexpr since C++20
  22
  23 #include <string>
  24 #include <cassert>
  25
  26 #include "test_macros.h"
  27 #include "test_allocator.h"
  28
  29 template <class T>
  30 struct some_alloc {
  31   typedef T value_type;
  32   some_alloc(const some_alloc&);
  33   T* allocate(std::size_t);
  34 };
  35
  36 template <class T>
  37 struct some_alloc2 {
  38   typedef T value_type;
  39
  40   some_alloc2() {}
  41   some_alloc2(const some_alloc2&);
  42   T* allocate(std::size_t);
  43   void deallocate(void*, unsigned) {}
  44
  45   typedef std::false_type propagate_on_container_move_assignment;
  46   typedef std::true_type is_always_equal;
  47 };
  48
  49 template <class T>
  50 struct some_alloc3 {
  51   typedef T value_type;
  52
  53   some_alloc3() {}
  54   some_alloc3(const some_alloc3&);
  55   T* allocate(std::size_t);
  56   void deallocate(void*, unsigned) {}
  57
  58   typedef std::false_type propagate_on_container_move_assignment;
  59   typedef std::false_type is_always_equal;
  60 };
  61
  62 TEST_CONSTEXPR_CXX20 bool test() {
  63   {
  64     typedef std::string C;
  65     static_assert(std::is_nothrow_move_assignable<C>::value, "");
  66   }
  67   {
  68     typedef std::basic_string<char, std::char_traits<char>, test_allocator<char>> C;
  69     static_assert(!std::is_nothrow_move_assignable<C>::value, "");
  70   }
  71   {
  72     typedef std::basic_string<char, std::char_traits<char>, some_alloc<char>> C;
  73 #if TEST_STD_VER > 14
  74     // if the allocators are always equal, then the move assignment can be noexcept
  75     static_assert(std::is_nothrow_move_assignable<C>::value, "");
  76 #else
  77     static_assert(!std::is_nothrow_move_assignable<C>::value, "");
  78 #endif
  79   }
  80 #if TEST_STD_VER > 14
  81   {
  82     //  POCMA is false, always equal
  83     typedef std::basic_string<char, std::char_traits<char>, some_alloc2<char>> C;
  84     static_assert(std::is_nothrow_move_assignable<C>::value, "");
  85   }
  86   {
  87     //  POCMA is false, not always equal
  88     typedef std::basic_string<char, std::char_traits<char>, some_alloc3<char>> C;
  89     static_assert(!std::is_nothrow_move_assignable<C>::value, "");
  90   }
  91 #endif
  92
  93   return true;
  94 }
  95
  96 int main(int, char**) {
  97   test();
  98 #if TEST_STD_VER > 17
  99   static_assert(test());
 100 #endif
 101
 102   return 0;
 103 }