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 // <memory>
10 
11 // weak_ptr
12 
13 // template<class Y> weak_ptr(const weak_ptr<Y>& r);
14 // template<class Y> weak_ptr(weak_ptr<Y>&& r);
15 //
16 // Regression test for https://github.com/llvm/llvm-project/issues/40459
17 // Verify that these constructors never attempt a derived-to-virtual-base
18 // conversion on a dangling weak_ptr.
19 
20 #include <cassert>
21 #include <cstring>
22 #include <memory>
23 #include <new>
24 #include <utility>
25 
26 #include "test_macros.h"
27 
28 struct A {
29   int i;
~AA30   virtual ~A() {}
31 };
32 struct B : public virtual A {
33   int j;
34 };
35 struct Deleter {
operator ()Deleter36   void operator()(void*) const {
37     // do nothing
38   }
39 };
40 
main(int,char **)41 int main(int, char**) {
42 #if TEST_STD_VER >= 11
43   alignas(B) char buffer[sizeof(B)];
44 #else
45   std::aligned_storage<sizeof(B), std::alignment_of<B>::value>::type buffer;
46 #endif
47   B* pb                 = ::new ((void*)&buffer) B();
48   std::shared_ptr<B> sp = std::shared_ptr<B>(pb, Deleter());
49   std::weak_ptr<B> wp   = sp;
50   sp                    = nullptr;
51   assert(wp.expired());
52 
53   // Overwrite the B object with junk.
54   std::memset(&buffer, '*', sizeof(buffer));
55 
56   std::weak_ptr<A> wq = wp;
57   assert(wq.expired());
58   std::weak_ptr<A> wr = std::move(wp);
59   assert(wr.expired());
60 
61   return 0;
62 }
63