gc.hpp: Start with initial bogus node

rt/include/typon/fundamental/gc.hpp

@@ -50,13 +50,16 @@ namespace typon::fdt::lock_free
     const uint _concurrency;
     std::atomic<u64> * const _stamps;
     std::atomic<u64> _stamp {0};
-    std::atomic<node *> _head {nullptr};
-    std::atomic<node *> _tail {nullptr};
+    std::atomic<node *> _head;
+    std::atomic<node *> _tail;
 
     gc(uint concurrency) noexcept
       : _concurrency(concurrency)
       , _stamps(new std::atomic<u64>[concurrency])
     {
+      auto first = new node(0);
+      _head.store(first);
+      _tail.store(first);
       for (uint i = 0; i < _concurrency; i++)
       {
         _stamps[i].store(u64(-1));
@@ -74,14 +77,7 @@ namespace typon::fdt::lock_free
       auto stamp = _stamp.load();
       auto node = new garbage<T> { ptr, stamp };
       auto head = _head.exchange(node);
-      if (head)
-      {
-        head->_next.store(node);
-      }
-      else
-      {
-        _tail.store(node);
-      }
+      head->_next.store(node);
     }
 
     void leave(uint id) noexcept
@@ -110,7 +106,7 @@ namespace typon::fdt::lock_free
     void reclaim(u64 oldest) noexcept
     {
       auto tail = _tail.load();
-      while (tail)
+      while (true)
       {
         if (tail->_stamp >= oldest)
         {
@@ -141,7 +137,6 @@ namespace typon::fdt::lock_free
       }
     }
   };
-
 }