[Bug c++/111028] Incorrect optimization with -o1,-o2

[ppalka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111028

--- Comment #3 from Patrick Palka <ppalka at gcc dot gnu.org> ---
Converting _node_offset from a pointer into an integer offset seems to fix the
testcase:

diff --git a/111028.C b/111028.C
index ed4106e..ef2b1be 100644
--- a/111028.C
+++ b/111028.C
@@ -15,7 +15,7 @@ class list_t
        public:
                list_t() { _head.next = _head.prev = &_head; }
                bool is_empty() const { return _head.next == &_head; }
-               T* entry(list_node_t &node) const { return &node == &_head ?
NULL : (T*)((char*)&node - (char*)_node_offset); }
+               T* entry(list_node_t &node) const { return &node == &_head ?
NULL : (T*)((char*)&node - _node_offset); }

                void add(T &node)
                {
@@ -37,11 +37,11 @@ class list_t
                }

        protected:
-               static list_node_t const * const _node_offset;
+               static size_t const _node_offset;
                list_node_t _head;
 };
 template <typename T, list_node_t T::*inner_list_node>
-list_node_t const * const list_t<T, inner_list_node>::_node_offset = &(((T
*)0)->*inner_list_node);
+size_t const list_t<T, inner_list_node>::_node_offset = size_t(&(((T
*)0)->*inner_list_node));

 template <typename T, list_node_t T::*inner_list_node>
 class safe_list_t: public list_t<T, inner_list_node>