-if (p->left != NULL) tree_walk(p->left, f, ctx);
-if (p->right != NULL) tree_walk(p->right, f, ctx);
+tree_walk(p->left, f, ctx);
+tree_walk(p->right, f, ctx);
+}
+
+
+
+/* Add a node to a tree, ignoring possibility of duplicates */
+
+static void
+tree_add_var(uschar * name, uschar * val, void * ctx)
+{
+tree_node ** root = ctx;
+tree_node * node = store_get(sizeof(tree_node) + Ustrlen(name), is_tainted(name));
+Ustrcpy(node->name, name);
+node->data.ptr = val;
+(void) tree_insertnode(root, node);