The code can be always rolled back to empty, no need to save the old …

…code.

Because it's not allowed to overwrite code now.

libethereum/State.cpp

@@ -518,7 +518,7 @@ bytes const& State::code(Address const& _addr) const
 
 void State::setCode(Address const& _address, bytes&& _code)
 {
-    m_changeLog.emplace_back(_address, code(_address));
+    m_changeLog.emplace_back(Change::Code, _address);
     m_cache[_address].setCode(std::move(_code));
 }
 
@@ -583,7 +583,7 @@ void State::rollback(size_t _savepoint)
             m_cache.erase(change.address);
             break;
         case Change::Code:
-            account.setCode(std::move(change.oldCode));
+            account.setCode(bytes{});
             break;
         case Change::Touch:
             account.untouch();

libethereum/State.h

@@ -116,7 +116,6 @@ struct Change
     Address address;  ///< Changed account address.
     u256 value;       ///< Change value, e.g. balance, storage and nonce.
     u256 key;         ///< Storage key. Last because used only in one case.
-    bytes oldCode;    ///< Code overwritten by CREATE, empty except in case of address collision.
 
     /// Helper constructor to make change log update more readable.
     Change(Kind _kind, Address const& _addr, u256 const& _value = 0):
@@ -134,11 +133,6 @@ struct Change
     Change(Address const& _addr, u256 const& _value):
             kind(Nonce), address(_addr), value(_value)
     {}
-
-    /// Helper constructor especially for new code change log.
-    Change(Address const& _addr, bytes const& _oldCode):
-            kind(Code), address(_addr), oldCode(_oldCode)
-    {}
 };
 
 using ChangeLog = std::vector<Change>;