|
145
|
1 // P0784R7
|
|
|
2 // { dg-do compile { target c++2a } }
|
|
|
3
|
|
|
4 namespace std
|
|
|
5 {
|
|
|
6 typedef __SIZE_TYPE__ size_t;
|
|
|
7
|
|
|
8 template <typename T>
|
|
|
9 struct allocator
|
|
|
10 {
|
|
|
11 constexpr allocator () noexcept {}
|
|
|
12
|
|
|
13 constexpr T *allocate (size_t n)
|
|
|
14 { return static_cast<T *> (::operator new (n * sizeof(T))); }
|
|
|
15
|
|
|
16 constexpr void
|
|
|
17 deallocate (T *p, size_t n)
|
|
|
18 { ::operator delete (p); }
|
|
|
19 };
|
|
|
20
|
|
|
21 template <typename T, typename U = T &&>
|
|
|
22 U __declval (int);
|
|
|
23 template <typename T>
|
|
|
24 T __declval (long);
|
|
|
25 template <typename T>
|
|
|
26 auto declval () noexcept -> decltype (__declval<T> (0));
|
|
|
27
|
|
|
28 template <typename T>
|
|
|
29 struct remove_reference
|
|
|
30 { typedef T type; };
|
|
|
31 template <typename T>
|
|
|
32 struct remove_reference<T &>
|
|
|
33 { typedef T type; };
|
|
|
34 template <typename T>
|
|
|
35 struct remove_reference<T &&>
|
|
|
36 { typedef T type; };
|
|
|
37
|
|
|
38 template <typename T>
|
|
|
39 constexpr T &&
|
|
|
40 forward (typename std::remove_reference<T>::type &t) noexcept
|
|
|
41 { return static_cast<T&&> (t); }
|
|
|
42
|
|
|
43 template<typename T>
|
|
|
44 constexpr T &&
|
|
|
45 forward (typename std::remove_reference<T>::type &&t) noexcept
|
|
|
46 { return static_cast<T&&> (t); }
|
|
|
47
|
|
|
48 template <typename T, typename... A>
|
|
|
49 constexpr auto
|
|
|
50 construct_at (T *l, A &&... a)
|
|
|
51 noexcept (noexcept (::new ((void *) 0) T (std::declval<A> ()...)))
|
|
|
52 -> decltype (::new ((void *) 0) T (std::declval<A> ()...))
|
|
|
53 { return ::new ((void *) l) T (std::forward<A> (a)...); }
|
|
|
54
|
|
|
55 template <typename T>
|
|
|
56 constexpr inline void
|
|
|
57 destroy_at (T *l)
|
|
|
58 { l->~T (); }
|
|
|
59 }
|
|
|
60
|
|
|
61 inline void *operator new (std::size_t, void *p) noexcept
|
|
|
62 { return p; }
|
|
|
63
|
|
|
64 constexpr bool
|
|
|
65 foo ()
|
|
|
66 {
|
|
|
67 std::allocator<int> a;
|
|
|
68 auto p = a.allocate (2);
|
|
|
69 std::construct_at (p, 1);
|
|
|
70 std::construct_at (p + 1, 2);
|
|
|
71 if (p[0] != 1 || p[1] != 2)
|
|
|
72 throw 1;
|
|
|
73 std::destroy_at (p);
|
|
|
74 std::destroy_at (p + 1);
|
|
|
75 a.deallocate (p, 2);
|
|
|
76 return true;
|
|
|
77 }
|
|
|
78
|
|
|
79 static_assert (foo ());
|
