#include <atomic>
#include <memory>

std::shared_ptr<T> pop()
{
    std::atomic<void*>& hp=get_hazard_pointer_for_current_thread();
    node* old_head=head.load();
    do
    {
        node* temp;
        do
        {
            temp=old_head;
            hp.store(old_head);
            old_head=head.load();
        } while(old_head!=temp);
    }
    while(old_head &&
          !head.compare_exchange_strong(old_head,old_head->next));
    hp.store(nullptr);
    std::shared_ptr<T> res;
    if(old_head)
    {
        res.swap(old_head->data);
        if(outstanding_hazard_pointers_for(old_head))
        {
            reclaim_later(old_head);
        }
        else
        {
            delete old_head;
        }
        delete_nodes_with_no_hazards();
    }
    return res;
}