[Bug c++/61421] Invalid -O2 optimization breaks program

[mimamer at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61421

--- Comment #11 from mimamer at gmail dot com ---
In short form,

template<class T> class list2
{
  public:
    struct node {
        T    *next;
        T    *prev;
    };

    node    anchor;

  public:
    /* API */
}

struct Obj : list2<Obj>::node {
    /* obj-specific elements */
}

list2<Obj>    main_list;

So, anchor is of type list2<Obj>::node while Obj is derived from
list2<Obj>::node.