Function ddsrt_avl_root_non_empty 

pub unsafe extern "C" fn ddsrt_avl_root_non_empty(
    td: *const ddsrt_avl_treedef_t,
    tree: *const ddsrt_avl_tree_t,
) -> *mut c_void

Same as @ref ddsrt_avl_root, but has undefined behavior in case the tree is empty.