Re: [boost] Could shared_ptr cause memory leak?

Subject: Re: [boost] Could shared_ptr cause memory leak?
From: Josh Juran (jjuran_at_[hidden])
Date: 2019-01-03 20:15:34

On Jan 3, 2019, at 2:25 PM, hh h via Boost <boost_at_[hidden]> wrote:

> Suppose I have a session object A, the shared_ptr<A> is created and
> stored in a global connection list after a connection is accepted by
> async_accept, when the connection is terminated, the reference in
> connection list is removed, but since A has a member B still holds A
> reference, that session object is never deleted, is it memory leak?
> 
> class A : public boost::enable_shared_from_this<A> {
> public:
>     A();
>     ~A();
>     void Start() {b = make_shared<B>(shared_from_this());}
>     void Stop();
> private:
>    shared_ptr<B> b;
> };

Yes, what you describe is a resource leak due to a reference loop foiling shared_ptr's RAII reference counting.

There are several ways to remedy this, one of which is to use a weak_ptr for one of the references.  Higher-risk options include making sure to break the reference loop manually, or using a raw pointer instead.

Josh