Creating weak_ptr<> from raw pointer

Question

I'd like to wrap raw pointer member to some smart pointer to prevent deleting inside a developing class. Owner of the object under pointer is outside of class. So, looks like boost::shared_ptr and std::auto_ptr does not fit. The following is a reduced example:

class Foo {
  boost::weak_ptr<Bar> m_bar;
public:
  void setBar(const Bar *bar) { // bar created on heap
    m_bar = bar;                // naturally compilation error
  }
};

Of course, it induces compilation error. What is a correct way to initialize weak_ptr from a raw pointer (if exist)?

Answer 1

The only way to do it is by getting hold of a shared_ptr or weak_ptr that owns the pointer, otherwise the weak_ptr has no way to find the existing owner in order to share ownership with it.

The only way to get a shared_ptr from a raw pointer that is already owned by another shared_ptr is if Bar derives from enable_shared_from_this<Bar>, then you can do

m_bar = bar->shared_from_this();