uniq_skiplist_grow set prev link correctly

src/tests/test_uniq_skiplist.c

@@ -228,15 +228,18 @@ static void test_reverse_iterator()
 {
     UniqSkiplistNode *node;
     int v;
+    int count;
     int *value;
 
-    v = 21;
+    printf("test_reverse_iterator\n");
+    count = 0;
+    v = 2;
     node = uniq_skiplist_find_ge_node(sl, &v);
     if (node != NULL) {
         while (node != sl->top) {
             value = (int *)node->data;
-            printf("value: %d\n", *value);
-            node = (UniqSkiplistNode *)LEVEL0_DOUBLE_CHAIN_PREV_LINK(node);
+            printf("value[%d]: %d\n", count++, *value);
+            node = UNIQ_SKIPLIST_LEVEL0_PREV_NODE(node);
         }
     }
 }

src/uniq_skiplist.c

@@ -236,8 +236,13 @@ static int uniq_skiplist_grow(UniqSkiplist *sl)
     sl->top_level_index = top_level_index;
 
     if (sl->factory->bidirection) {
-        LEVEL0_DOUBLE_CHAIN_TAIL(sl) =
-            LEVEL0_DOUBLE_CHAIN_PREV_LINK(old_top);
+        if (top->links[0] != sl->factory->tail) {  //not empty
+            LEVEL0_DOUBLE_CHAIN_PREV_LINK(top->links[0]) = top;
+            LEVEL0_DOUBLE_CHAIN_TAIL(sl) =
+                LEVEL0_DOUBLE_CHAIN_PREV_LINK(old_top);
+        } else {
+            LEVEL0_DOUBLE_CHAIN_TAIL(sl) = sl->top;
+        }
     }
 
     UNIQ_SKIPLIST_FREE_MBLOCK_OBJECT(sl, old_top_level_index, old_top);