They are used, but cppcheck is probably confused about use from friend
class and templates. I'd be confused myself and I'm not written in C++,
so it is excused.
/// the top node
///
/// \exception None
+ // cppcheck-suppress unusedPrivateFunction (false positive, it is used)
void pop() {
assert(!isEmpty());
--level_count_;
/// otherwise the node should be the root node of DomainTree.
///
/// \exception None
+ // cppcheck-suppress unusedPrivateFunction (false positive, it is used)
void push(const DomainTreeNode<T>* node) {
assert(level_count_ < RBT_MAX_LEVEL);
nodes_[level_count_++] = node;