avl_tree.h: avoid bad function pointer cast

Casting the type of the 'cmp' function, while under normal circumstances
compiled correctly, was not technically correct and was not compatible
with some control flow integrity (CFI) implementations.

diff --git a/include/wimlib/avl_tree.h b/include/wimlib/avl_tree.h
index ed615edc3931e9646dac5af5ab6adf9174c6bf02..b7a9bb1b27fb3958bc8734cb160f36944d66981c 100644 (file)
--- a/include/wimlib/avl_tree.h
+++ b/include/wimlib/avl_tree.h
@@ -145,10 +145,18 @@ avl_tree_lookup_node(const struct avl_tree_node *root,
                     int (*cmp)(const struct avl_tree_node *,
                                const struct avl_tree_node *))
 {
                     int (*cmp)(const struct avl_tree_node *,
                                const struct avl_tree_node *))
 {

-       return avl_tree_lookup(root,
-                              (const void *)node,
-                              (int (*) (const void *,
-                                        const struct avl_tree_node *))cmp);
+       const struct avl_tree_node *cur = root;
+
+       while (cur) {
+               int res = (*cmp)(node, cur);
+               if (res < 0)
+                       cur = cur->left;
+               else if (res > 0)
+                       cur = cur->right;
+               else
+                       break;
+       }
+       return (struct avl_tree_node*)cur;

 }
 
 /*
 }
 
 /*