core,state: some refactors

core/state/state_object.go

@@ -392,9 +392,9 @@ func (s *stateObject) updateRoot(db Database) {
 	s.data.Root = s.trie.Hash()
 }
 
-// CommitTrie the storage trie of the object to db.
-// This updates the trie root.
-func (s *stateObject) CommitTrie(db Database) (*trie.NodeSet, error) {
+// commitTrie submits the storage changes into the storage trie and re-computes
+// the root. Besides, all trie changes will be collected in a nodeset and returned.
+func (s *stateObject) commitTrie(db Database) (*trie.NodeSet, error) {
 	// If nothing changed, don't bother with hashing anything
 	if s.updateTrie(db) == nil {
 		return nil, nil

core/state/statedb.go

@@ -986,7 +986,7 @@ func (s *StateDB) Commit(deleteEmptyObjects bool) (common.Hash, error) {
 				obj.dirtyCode = false
 			}
 			// Write any storage changes in the state object to its storage trie
-			nodeSet, err := obj.CommitTrie(s.db)
+			nodeSet, err := obj.commitTrie(s.db)
 			if err != nil {
 				return common.Hash{}, err
 			}
@@ -1000,6 +1000,12 @@ func (s *StateDB) Commit(deleteEmptyObjects bool) (common.Hash, error) {
 			}
 		}
 	}
+	// If the contract is destructed, the storage is still left in the
+	// database as dangling data. Theoretically it's should be wiped from
+	// database as well, but in hash-based-scheme it's extremely hard to
+	// determine that if the trie nodes are also referenced by other storage,
+	// and in path-based-scheme some technical challenges are still unsolved.
+	// Although it won't affect the correctness but please fix it TODO(rjl493456442).
 	if len(s.stateObjectsDirty) > 0 {
 		s.stateObjectsDirty = make(map[common.Address]struct{})
 	}