1 //===----------------------------------------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is dual licensed under the MIT and the University of Illinois Open
6 // Source Licenses. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 // <memory>
11 
12 // weak_ptr
13 
14 // template<class Y> weak_ptr(const weak_ptr<Y>& r);
15 // template<class Y> weak_ptr(weak_ptr<Y> &&r);
16 
17 #include <memory>
18 #include <type_traits>
19 #include <cassert>
20 
21 struct B
22 {
23     static int count;
24 
BB25     B() {++count;}
BB26     B(const B&) {++count;}
~BB27     virtual ~B() {--count;}
28 };
29 
30 int B::count = 0;
31 
32 struct A
33     : public B
34 {
35     static int count;
36 
AA37     A() {++count;}
AA38     A(const A&) {++count;}
~AA39     ~A() {--count;}
40 };
41 
42 int A::count = 0;
43 
44 struct C
45 {
46     static int count;
47 
CC48     C() {++count;}
CC49     C(const C&) {++count;}
~CC50     virtual ~C() {--count;}
51 };
52 
53 int C::count = 0;
54 
55 template <class T>
source(std::shared_ptr<T> p)56 std::weak_ptr<T> source (std::shared_ptr<T> p) { return std::weak_ptr<T>(p); }
57 
main()58 int main()
59 {
60     static_assert(( std::is_convertible<std::weak_ptr<A>, std::weak_ptr<B> >::value), "");
61     static_assert((!std::is_convertible<std::weak_ptr<B>, std::weak_ptr<A> >::value), "");
62     static_assert((!std::is_convertible<std::weak_ptr<A>, std::weak_ptr<C> >::value), "");
63     {
64         const std::weak_ptr<A> pA(std::shared_ptr<A>(new A));
65         assert(pA.use_count() == 0);
66         assert(B::count == 0);
67         assert(A::count == 0);
68         {
69             std::weak_ptr<B> pB(pA);
70             assert(B::count == 0);
71             assert(A::count == 0);
72             assert(pB.use_count() == 0);
73             assert(pA.use_count() == 0);
74         }
75         assert(pA.use_count() == 0);
76         assert(B::count == 0);
77         assert(A::count == 0);
78     }
79     assert(B::count == 0);
80     assert(A::count == 0);
81     {
82         std::weak_ptr<A> pA;
83         assert(pA.use_count() == 0);
84         assert(B::count == 0);
85         assert(A::count == 0);
86         {
87             std::weak_ptr<B> pB(pA);
88             assert(B::count == 0);
89             assert(A::count == 0);
90             assert(pB.use_count() == 0);
91             assert(pA.use_count() == 0);
92         }
93         assert(pA.use_count() == 0);
94         assert(B::count == 0);
95         assert(A::count == 0);
96     }
97     assert(B::count == 0);
98     assert(A::count == 0);
99 
100     {
101         std::shared_ptr<A> ps(new A);
102         std::weak_ptr<A> pA = source(ps);
103         std::weak_ptr<B> pB(std::move(pA));
104         assert(pB.use_count() == 1);
105     }
106     assert(B::count == 0);
107     assert(A::count == 0);
108 }
109