From 81207490bf774b87ab5411e14ededc4c2145406c Mon Sep 17 00:00:00 2001
From: Gary Rong <garyrong0905@gmail.com>
Date: Tue, 15 Mar 2022 14:35:18 +0800
Subject: [PATCH 1/4] trie: fix the memory leak in trie iterator

In trie iterator a batch of live nodes will be tracked and be poped
when it's iterated. However the poped node state should be explictly
set to nil in order to be garbage collected.
---
 trie/iterator.go | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/trie/iterator.go b/trie/iterator.go
index 1fbf991af09e..1bf3e75231c7 100644
--- a/trie/iterator.go
+++ b/trie/iterator.go
@@ -425,7 +425,7 @@ func findChild(n *fullNode, index int, path []byte, ancestor common.Hash) (node,
 func (it *nodeIterator) nextChild(parent *nodeIteratorState, ancestor common.Hash) (*nodeIteratorState, []byte, bool) {
 	switch node := parent.node.(type) {
 	case *fullNode:
-		//Full node, move to the first non-nil child.
+		// Full node, move to the first non-nil child.
 		if child, state, path, index := findChild(node, parent.index+1, it.path, ancestor); child != nil {
 			parent.index = index - 1
 			return state, path, true
@@ -503,8 +503,9 @@ func (it *nodeIterator) push(state *nodeIteratorState, parentIndex *int, path []
 }
 
 func (it *nodeIterator) pop() {
-	parent := it.stack[len(it.stack)-1]
-	it.path = it.path[:parent.pathlen]
+	last := it.stack[len(it.stack)-1]
+	it.path = it.path[:last.pathlen]
+	it.stack[len(it.stack)-1] = nil
 	it.stack = it.stack[:len(it.stack)-1]
 }
 

From c5d78fa0491a900af6f7045b09484f1b36584767 Mon Sep 17 00:00:00 2001
From: Gary Rong <garyrong0905@gmail.com>
Date: Tue, 15 Mar 2022 14:43:42 +0800
Subject: [PATCH 2/4] trie: fix empty trie iterator

---
 trie/iterator.go      |  8 +++++---
 trie/iterator_test.go | 14 ++++++++++++++
 2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/trie/iterator.go b/trie/iterator.go
index 1bf3e75231c7..b0b7ce0d5881 100644
--- a/trie/iterator.go
+++ b/trie/iterator.go
@@ -20,7 +20,6 @@ import (
 	"bytes"
 	"container/heap"
 	"errors"
-
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/ethdb"
 )
@@ -154,8 +153,11 @@ func (e seekError) Error() string {
 }
 
 func newNodeIterator(trie *Trie, start []byte) NodeIterator {
-	if trie.Hash() == emptyState {
-		return new(nodeIterator)
+	if trie.Hash() == emptyRoot {
+		return &nodeIterator{
+			trie: trie,
+			err:  errIteratorEnd,
+		}
 	}
 	it := &nodeIterator{trie: trie}
 	it.err = it.seek(start)
diff --git a/trie/iterator_test.go b/trie/iterator_test.go
index 1a9a5e80e588..53bdd39200b1 100644
--- a/trie/iterator_test.go
+++ b/trie/iterator_test.go
@@ -29,6 +29,20 @@ import (
 	"github.com/ethereum/go-ethereum/ethdb/memorydb"
 )
 
+func TestEmptyIterator(t *testing.T) {
+	trie := newEmpty()
+	iter := trie.NodeIterator(nil)
+
+	seen := make(map[string]struct{})
+	for iter.Next(true) {
+		seen[string(iter.Path())] = struct{}{}
+		fmt.Println("iter.path", iter.Path(), "val", iter.NodeBlob())
+	}
+	if len(seen) != 0 {
+		t.Fatal("Unexpected trie node iterated")
+	}
+}
+
 func TestIterator(t *testing.T) {
 	trie := newEmpty()
 	vals := []struct{ k, v string }{

From f7ef780f5f65b6ee4d4bf0ac52ffa536a238eaa2 Mon Sep 17 00:00:00 2001
From: Gary Rong <garyrong0905@gmail.com>
Date: Tue, 15 Mar 2022 14:47:58 +0800
Subject: [PATCH 3/4] trie: fix goimport

---
 trie/iterator.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/trie/iterator.go b/trie/iterator.go
index b0b7ce0d5881..e0006ee05e3b 100644
--- a/trie/iterator.go
+++ b/trie/iterator.go
@@ -20,6 +20,7 @@ import (
 	"bytes"
 	"container/heap"
 	"errors"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/ethdb"
 )

From 8c95e750e1a1e94c5a9603acdf4d8ede1aa93b5a Mon Sep 17 00:00:00 2001
From: Gary Rong <garyrong0905@gmail.com>
Date: Tue, 15 Mar 2022 16:14:31 +0800
Subject: [PATCH 4/4] trie: remove debug line

---
 trie/iterator_test.go | 1 -
 1 file changed, 1 deletion(-)

diff --git a/trie/iterator_test.go b/trie/iterator_test.go
index 53bdd39200b1..9a46e9b99548 100644
--- a/trie/iterator_test.go
+++ b/trie/iterator_test.go
@@ -36,7 +36,6 @@ func TestEmptyIterator(t *testing.T) {
 	seen := make(map[string]struct{})
 	for iter.Next(true) {
 		seen[string(iter.Path())] = struct{}{}
-		fmt.Println("iter.path", iter.Path(), "val", iter.NodeBlob())
 	}
 	if len(seen) != 0 {
 		t.Fatal("Unexpected trie node iterated")