How do circular references affect shared_ptr in C++?

What are circular references in C++ and how do they affect shared_ptr?

Circular references occur when two or more objects reference each other, creating a cycle. In C++, this can lead to memory leaks when using shared_ptr, as the reference count never reaches zero.

How can I avoid circular references when using shared_ptr?

To avoid circular references, you can use weak_ptr for one of the references in the cycle. This way, the reference count won't prevent the objects from being deleted.

Can you give me an example of using weak_ptr to break a circular reference?

Sure! If you have two classes, A and B, where A holds a shared_ptr to B and B holds a shared_ptr to A, you can change B's pointer to a weak_ptr. This breaks the cycle and allows both objects to be deleted when they go out of scope.

What happens if I forget to use weak_ptr?

If you forget to use weak_ptr, the circular reference will prevent the reference counts from reaching zero, leading to memory leaks as the objects will never be destroyed.