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


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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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Avsnitt 3. Kapitel 3

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C++ Smart Pointers

1. Introduction to Smart Pointers

Understanding Pointers Dynamic memory allocation The Need For Smart Pointers

2. Unique Pointers

Introduction to Unique Pointers Moving Unique Pointers Application For Unique Pointers Passing Around Unique Pointers Methods of a Unique Pointer

3. Shared Pointers

Introduction to Shared Pointers Creating and Sharing Shared Pointers Circular References and Shared Pointers

4. Weak Pointers

Introduction to Weak Pointers Creating And Using Weak Pointers Breaking Circular References With Weak Pointers Important Weak Pointer Functions

5. Advanced topics