core/state: simplify codechange journalling

Author: holiman

core/state/journal.go

@@ -18,6 +18,7 @@ package state
 
 import (
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/holiman/uint256"
 )
 
@@ -145,12 +146,10 @@ func (j *journal) JournalBalanceChange(addr common.Address, previous *uint256.In
 	})
 }
 
-func (j *journal) JournalSetCode(address common.Address, prevcode, prevHash []byte) {
-	j.append(codeChange{
-		account:  &address,
-		prevhash: prevHash,
-		prevcode: prevcode,
-	})
+// JournalSetCode journals the setting of code: it is implicit that the previous
+// values were "no code" and emptyCodeHash.
+func (j *journal) JournalSetCode(address common.Address) {
+	j.append(codeChange{account: &address})
 }
 
 func (j *journal) JournalNonceChange(address common.Address, prev uint64) {
@@ -228,8 +227,7 @@ type (
 		key, prevalue common.Hash
 	}
 	codeChange struct {
-		account            *common.Address
-		prevcode, prevhash []byte
+		account *common.Address
 	}
 
 	// Changes to other state values.
@@ -330,7 +328,7 @@ func (ch nonceChange) dirtied() *common.Address {
 }
 
 func (ch codeChange) revert(s *StateDB) {
-	s.getStateObject(*ch.account).setCode(common.BytesToHash(ch.prevhash), ch.prevcode)
+	s.getStateObject(*ch.account).setCode(types.EmptyCodeHash, nil)
 }
 
 func (ch codeChange) dirtied() *common.Address {

core/state/state_object.go

@@ -488,7 +488,7 @@ func (s *stateObject) CodeSize() int {
 }
 
 func (s *stateObject) SetCode(codeHash common.Hash, code []byte) {
-	s.db.journal.JournalSetCode(s.address, s.Code(), s.CodeHash())
+	s.db.journal.JournalSetCode(s.address)
 	s.setCode(codeHash, code)
 }
 

core/state/statedb_test.go

@@ -296,6 +296,12 @@ func newTestAction(addr common.Address, r *rand.Rand) testAction {
 		{
 			name: "SetCode",
 			fn: func(a testAction, s *StateDB) {
+				// SetCode can only be performed in case the addr does
+				// not already hold code
+				if c := s.GetCode(addr); len(c) > 0 {
+					// no-op
+					return
+				}
 				code := make([]byte, 16)
 				binary.BigEndian.PutUint64(code, uint64(a.args[0]))
 				binary.BigEndian.PutUint64(code[8:], uint64(a.args[1]))