final/test/utilities/memory/util.smartptr/util.smartptr.shared/util.smartptr.shared.cast/dynamic_pointer_cast.pass.cpp

//===----------------------------------------------------------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is dual licensed under the MIT and the University of Illinois Open
// Source Licenses. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

// <memory>

// shared_ptr

// template<class T, class U> shared_ptr<T> dynamic_pointer_cast(const shared_ptr<U>& r);

#include <memory>
#include <type_traits>
#include <cassert>

struct B
{
    static int count;

    B() {++count;}
    B(const B&) {++count;}
    virtual ~B() {--count;}
};

int B::count = 0;

struct A
    : public B
{
    static int count;

    A() {++count;}
    A(const A&) {++count;}
    ~A() {--count;}
};

int A::count = 0;

int main()
{
    {
        const std::shared_ptr<B> pB(new A);
        std::shared_ptr<A> pA = std::dynamic_pointer_cast<A>(pB);
        assert(pA.get() == pB.get());
        assert(!pB.owner_before(pA) && !pA.owner_before(pB));
    }
    {
        const std::shared_ptr<B> pB(new B);
        std::shared_ptr<A> pA = std::dynamic_pointer_cast<A>(pB);
        assert(pA.get() == 0);
        assert(pA.use_count() == 0);
    }
}