In member function 'void LinkList::Clear()',
    inlined from 'void LinkList::Copy(const LinkList&)' at /in/foo.cc:16:14,
    inlined from 'LinkList::LinkList(const LinkList&)' at /in/foo.cc:29:13,
    inlined from 'int main()' at /in/foo.cc:94:19:
/in/foo.cc:36:16: warning: 'L2.LinkList::head' may be used uninitialized [-Wmaybe-uninitialized]
   36 |         while (head != NULL)
      |                ^~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:94:14: note: 'L2' declared here
   94 |     LinkList L2(L1);
      |              ^~