core/state, eth: Updated suicides objects when tracing transactions

Consensus rules dictate that objects can only be removed during the
finalisation of the transaction (i.e. after all calls have finished).
Thus calling a suicided contract twice from the same transaction:
A->B(S)->ret(A)->B(S) results in 2 suicides. Calling the suicided
object twice from two transactions: A->B(S), A->B, results in only one
suicide and a call to an empty object.

Our current debug tracing functionality replays all transaction that
were executed prior to the targetted transaction in order to provide
the user with an accurate trace.

As a side effect to calling StateDB.IntermediateRoot it also deletes any
suicides objects. Our tracing code never calls this function because it
isn't interested in the intermediate root. Becasue of this it caused a
bug in the tracing code where transactions that were send to priviously
deleted objects resulted in two suicides rather than one suicide and a
call to an empty object.

Fixes #2542

core/state/statedb.go

@@ -370,6 +370,27 @@ func (s *StateDB) IntermediateRoot() common.Hash {
 	return s.trie.Hash()
 }
 
+// DeleteSuicides flags the suicided objects for deletion so that it
+// won't be referenced again when called / queried up on.
+//
+// DeleteSuicides should not be used for consensus related updates
+// under any circumstances.
+func (s *StateDB) DeleteSuicides() {
+	// Reset refund so that any used-gas calculations can use
+	// this method.
+	s.refund = new(big.Int)
+	for _, stateObject := range s.stateObjects {
+		if stateObject.dirty {
+			// If the object has been removed by a suicide
+			// flag the object as deleted.
+			if stateObject.remove {
+				stateObject.deleted = true
+			}
+			stateObject.dirty = false
+		}
+	}
+}
+
 // Commit commits all state changes to the database.
 func (s *StateDB) Commit() (root common.Hash, err error) {
 	root, batch := s.CommitBatch()

eth/api.go

@@ -1876,6 +1876,7 @@ func (api *PrivateDebugAPI) TraceTransaction(txHash common.Hash, logger *vm.LogC
 			if err != nil {
 				return nil, fmt.Errorf("mutation failed: %v", err)
 			}
+			stateDb.DeleteSuicides()
 			continue
 		}
 		// Otherwise trace the transaction and return