Initialize a boost::shared_ptr to NULL

Question

Can I initialize shared_ptr with NULL value?

boost::shared_ptr<Type> s_obj(NULL);

If not, then how?

Answer 1

The default construction does this for you:

template<class T> class shared_ptr
{
public:

    explicit shared_ptr(T * p = 0): px(p)
    { 
        //Snip
    }

    //...

private:

    T * px;            // contained pointer
    count_type * pn;   // ptr to reference counter
};

Answer 2

That's the default construction, i.e.:

boost::shared_ptr<Type> s_obj;

s_obj now holds a null pointer and evaluates to boolean false when truth-tested;