Talbot, George wrote:

Hi,

I have a question for the designers and implementers of boost::shared_ptr:

Is there any plan afoot to support lock-free programming using shared_ptr? I was fooling around with wanting to attempt lock-free update of a tree structure that I have that uses shared_ptr. If no-one's thinking about this, how might I go about implementing:

bool boost::shared_ptr<T>::compare_and_swap(T* original, shared_ptr<T>& new_one)

Very, very difficult. :-) shared_ptr is not atomic; you can look at Joe Seigh's atomic_ptr: http://atomic-ptr-plus.sourceforge.net/ and Chris Thomasson's http://appcore.home.comcast.net/vzoom/refcount/ for examples of atomic reference counted pointers. Shared_ptr can be made atomic by using a spinlock. This isn't really lock-free, though.