add original source

source/listing_7.4.cpp

@@ -0,0 +1,25 @@
+#include <atomic>
+#include <memory>
+
+template<typename T>
+class lock_free_stack
+{
+private:
+    std::atomic<unsigned> threads_in_pop;
+    void try_reclaim(node* old_head);
+public:
+    std::shared_ptr<T> pop()
+    {
+        ++threads_in_pop;
+        node* old_head=head.load();
+        while(old_head &&
+              !head.compare_exchange_weak(old_head,old_head->next));
+        std::shared_ptr<T> res;
+        if(old_head)
+        {
+            res.swap(old_head->data);
+        }
+        try_reclaim(old_head);
+        return res;
+    }
+};