NFD » ndn-cxx

each identity is maintained in the PIB's IdentityContainer, which provides shared pointer to the identity instance as handle for others

It's unnecessary to expose shared_ptr in public API.

Instead:

class Identity // copyable
{
public:
  explicit operator bool() const; ///< valid (not deleted)
  bool operator!() const; ///< deleted

  const Name& getName() const; ///< identity name

  // (other getters)

private:
  weak_ptr<detail::IdentityImpl> m_impl;
};

namespace detail {
class IdentityImpl;
} // namespace detail

class IdentityContainer : noncopyable
{
public:
  Identity getIdentity(..) const;

private:
  std::container<shared_ptr<detail::IdentityImpl>> m_container;
};

I think you are right, weak_pointer is a better approach. actually shared_ptr does not address the issue completely. I will use weak_ptr in implementation.