Right pad bytes to prevent future programmers making bugs

vm/memory.go

@@ -1,6 +1,10 @@
 package vm
 
-import "fmt"
+import (
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
+)
 
 type Memory struct {
 	store []byte
@@ -11,7 +15,8 @@ func NewMemory() *Memory {
 }
 
 func (m *Memory) Set(offset, size uint64, value []byte) {
-	if len(value) > 0 {
+	value = common.RightPadBytes(value, int(size))
+
 	totSize := offset + size
 	lenSize := uint64(len(m.store) - 1)
 	if totSize > lenSize {
@@ -26,7 +31,6 @@ func (m *Memory) Set(offset, size uint64, value []byte) {
 	}
 	copy(m.store[offset:offset+size], value)
 }
-}
 
 func (m *Memory) Resize(size uint64) {
 	if uint64(m.Len()) < size {