c++ - Memory leak in linked list of strings -

I have created a templated doubly linked list. In my destructor I delete all the nodes. I do not have memory leaks with any priority, but if I have created a link list of std :: string then I have leaked. I'm not sure how to handle it.

  node_pointer next (first); First = first-> _next; Delete next;  

I call up while looping through a written list.

I resolved my issue that I ended up destroying virtualization. As soon as I put virtual keywords, the memory leaked went away.