Index: lib/core/include/Graph.h
===================================================================
--- lib/core/include/Graph.h	(revision 2d2406947d3035c7c043b8ce3d4ba7eac0461b46)
+++ lib/core/include/Graph.h	(revision a486fb206b1a32d7cbfec6fa9d5c30d74f0f0801)
@@ -702,22 +702,27 @@
    Table& operator= (const Table& t)
    {
       this->~Table();
       new(this) Table(t);
       return *this;
    }
 
    void swap(Table& t)
    {
       std::swap(R,t.R);
+#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ >= 7
+      node_maps.swap(t.node_maps);
+      edge_maps.swap(t.edge_maps);
+#else
       std::swap(node_maps, t.node_maps);
       std::swap(edge_maps, t.edge_maps);
+#endif
       std::swap(n_nodes, t.n_nodes);
       std::swap(free_node_id, t.free_node_id);
       std::swap(free_edge_ids, t.free_edge_ids);
       for (auto& map : node_maps)
          map._table=this;
       for (auto& map : t.node_maps)
          map._table=&t;
       for (auto& map : edge_maps)
          map._table=this;
       for (auto& map : t.edge_maps)