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Lære Circular References and Shared Pointers | Shared Pointers
C++ Smart Pointers

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Circular References and Shared Pointers

When working with std::shared_ptr, you might encounter an issue known as a circular reference. A circular reference occurs when two objects hold shared_ptr references to each other. Since shared_ptr uses reference counting, the count never reaches zero, causing a memory leak.

main.cpp

main.cpp

copy
#include <iostream>
#include <memory>

class B; // Forward declaration

class A {
public:
std::shared_ptr<B> p_b;
~A() { std::cout << "A destroyed\n"; }
};

class B {
public:
~B() { std::cout << "B destroyed\n"; }

std::shared_ptr<A> p_a;
};

int main()
{
std::shared_ptr<A> a = std::make_shared<A>();
std::shared_ptr<B> b = std::make_shared<B>();

a->p_b = b;
b->p_a = a;
}
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#include <iostream> #include <memory> class B; // Forward declaration class A { public: std::shared_ptr<B> p_b; ~A() { std::cout << "A destroyed\n"; } }; class B { public: ~B() { std::cout << "B destroyed\n"; } std::shared_ptr<A> p_a; }; int main() { std::shared_ptr<A> a = std::make_shared<A>(); std::shared_ptr<B> b = std::make_shared<B>(); a->p_b = b; b->p_a = a; }

There is a way to fix this issue you need to use a different type of smart pointer.

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What problem does a circular reference cause in std::shared_ptr?

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