Add a notion of zombies to preserve empty account behavior

core/state/journal.go

@@ -40,13 +40,17 @@ type journalEntry interface {
 // commit. These are tracked to be able to be reverted in the case of an execution
 // exception or request for reversal.
 type journal struct {
+	zombieEntries map[common.Address]int // Arbitrum: number of createZombieChange entries for each address
+
 	entries []journalEntry         // Current changes tracked by the journal
 	dirties map[common.Address]int // Dirty accounts and the number of changes
 }
 
 // newJournal creates a new initialized journal.
 func newJournal() *journal {
 	return &journal{
+		zombieEntries: make(map[common.Address]int),
+
 		dirties: make(map[common.Address]int),
 	}
 }
@@ -56,6 +60,10 @@ func (j *journal) append(entry journalEntry) {
 	j.entries = append(j.entries, entry)
 	if addr := entry.dirtied(); addr != nil {
 		j.dirties[*addr]++
+		// Arbitrum: also track the number of zombie changes
+		if isZombie(entry) {
+			j.zombieEntries[*addr]++
+		}
 	}
 }
 
@@ -70,6 +78,13 @@ func (j *journal) revert(statedb *StateDB, snapshot int) {
 		if addr := j.entries[i].dirtied(); addr != nil {
 			if j.dirties[*addr]--; j.dirties[*addr] == 0 {
 				delete(j.dirties, *addr)
+
+				// Revert zombieEntries tracking
+				if isZombie(j.entries[i]) {
+					if j.zombieEntries[*addr]--; j.zombieEntries[*addr] == 0 {
+						delete(j.zombieEntries, *addr)
+					}
+				}
 			}
 		}
 	}
@@ -95,6 +110,8 @@ func (j *journal) copy() *journal {
 		entries = append(entries, j.entries[i].copy())
 	}
 	return &journal{
+		zombieEntries: maps.Clone(j.zombieEntries),
+
 		entries: entries,
 		dirties: maps.Clone(j.dirties),
 	}
@@ -106,6 +123,11 @@ type (
 		account *common.Address
 	}
 
+	// Changes to the account trie without being marked as dirty.
+	createZombieChange struct {
+		account *common.Address
+	}
+
 	// createContractChange represents an account becoming a contract-account.
 	// This event happens prior to executing initcode. The journal-event simply
 	// manages the created-flag, in order to allow same-tx destruction.

core/state/journal_arbitrum.go

@@ -77,3 +77,33 @@ func (ch EvictWasm) copy() journalEntry {
 		Debug:      ch.Debug,
 	}
 }
+
+// Arbitrum: only implemented by createZombieChange
+type possibleZombie interface {
+	// Arbitrum: return true if this change should, on its own, create an empty account.
+	// If combined with another non-zombie change the empty account will be cleaned up.
+	isZombie() bool
+}
+
+func isZombie(entry journalEntry) bool {
+	possiblyZombie, isPossiblyZombie := entry.(possibleZombie)
+	return isPossiblyZombie && possiblyZombie.isZombie()
+}
+
+func (ch createZombieChange) revert(s *StateDB) {
+	delete(s.stateObjects, *ch.account)
+}
+
+func (ch createZombieChange) dirtied() *common.Address {
+	return ch.account
+}
+
+func (ch createZombieChange) copy() journalEntry {
+	return createZombieChange{
+		account: ch.account,
+	}
+}
+
+func (ch createZombieChange) isZombie() bool {
+	return true
+}

core/state/journal_arbitrum_test.go

@@ -0,0 +1,14 @@
+package state
+
+import "testing"
+
+func TestIsZombie(t *testing.T) {
+	var nonZombie journalEntry = createObjectChange{}
+	if isZombie(nonZombie) {
+		t.Error("createObjectChange should not be a zombie")
+	}
+	var zombie journalEntry = createZombieChange{}
+	if !isZombie(zombie) {
+		t.Error("createZombieChange should be a zombie")
+	}
+}

core/state/statedb.go

@@ -436,6 +436,11 @@ func (s *StateDB) AddBalance(addr common.Address, amount *uint256.Int, reason tr
 
 // SubBalance subtracts amount from the account associated with addr.
 func (s *StateDB) SubBalance(addr common.Address, amount *uint256.Int, reason tracing.BalanceChangeReason) {
+	// Arbitrum: this behavior created empty accounts in old geth versions.
+	if amount.IsZero() && s.getStateObject(addr) == nil {
+		s.createZombie(addr)
+		return
+	}
 	stateObject := s.getOrNewStateObject(addr)
 	if stateObject != nil {
 		s.arbExtraData.unexpectedBalanceDelta.Sub(s.arbExtraData.unexpectedBalanceDelta, amount.ToBig())
@@ -695,6 +700,15 @@ func (s *StateDB) createObject(addr common.Address) *stateObject {
 	return obj
 }
 
+// createObject creates a new state object. The assumption is held there is no
+// existing account with the given address, otherwise it will be silently overwritten.
+func (s *StateDB) createZombie(addr common.Address) *stateObject {
+	obj := newObject(s, addr, nil)
+	s.journal.append(createZombieChange{account: &addr})
+	s.setStateObject(obj)
+	return obj
+}
+
 // CreateAccount explicitly creates a new state object, assuming that the
 // account did not previously exist in the state. If the account already
 // exists, this function will silently overwrite it which might lead to a
@@ -842,7 +856,8 @@ func (s *StateDB) GetRefund() uint64 {
 // into the tries just yet. Only IntermediateRoot or Commit will do that.
 func (s *StateDB) Finalise(deleteEmptyObjects bool) {
 	addressesToPrefetch := make([][]byte, 0, len(s.journal.dirties))
-	for addr := range s.journal.dirties {
+	for addr, dirtyCount := range s.journal.dirties {
+		isZombie := s.journal.zombieEntries[addr] == dirtyCount
 		obj, exist := s.stateObjects[addr]
 		if !exist {
 			// ripeMD is 'touched' at block 1714175, in tx 0x1237f737031e40bcde4a8b7e717b2d15e3ecadfe49bb1bbc71ee9deb09c6fcf2
@@ -853,7 +868,7 @@ func (s *StateDB) Finalise(deleteEmptyObjects bool) {
 			// Thus, we can safely ignore it here
 			continue
 		}
-		if obj.selfDestructed || (deleteEmptyObjects && obj.empty()) {
+		if obj.selfDestructed || (deleteEmptyObjects && obj.empty() && !isZombie) {
 			delete(s.stateObjects, obj.address)
 			s.markDelete(addr)