Check parent pointers

ConflictSet.cpp

@@ -349,6 +349,19 @@ void rotate(Node **node, bool dir) {
   updateMaxVersion(l);
 }
 
+void checkParentPointers(Node *node, bool &success) {
+  for (int i = 0; i < 2; ++i) {
+    if (node->child[i] != nullptr) {
+      if (node->child[i]->parent != node) {
+        fprintf(stderr, "%.*s child %d has parent pointer %p. Expected %p\n",
+                node->len, (const char *)(node + 1), i,
+                (void *)node->child[i]->parent, (void *)node);
+      }
+      checkParentPointers(node->child[i], success);
+    }
+  }
+}
+
 int64_t checkMaxVersion(Node *node, bool &success) {
   int64_t expected = std::max(node->pointVersion, node->rangeVersion);
   for (int i = 0; i < 2; ++i) {
@@ -385,6 +398,7 @@ bool checkInvariants(Node *node) {
   assert(std::is_sorted(keys.begin(), keys.end()));
 
   checkMaxVersion(node, success);
+  checkParentPointers(node, success);
 
   // TODO Compare logical contents of map with
   // reference implementation