Avoid memneed overflow

libevm/VM.h

@@ -173,15 +173,15 @@ template <class Ext> dev::bytesConstRef dev::eth::VM::go(Ext& _ext, OnOpFunc con
 		// These all operate on memory and therefore potentially expand it:
 		case Instruction::MSTORE:
 			require(2);
-			newTempSize = m_stack.back() + 32;
+            newTempSize = (bigint)m_stack.back() + 32;
 			break;
 		case Instruction::MSTORE8:
 			require(2);
-			newTempSize = m_stack.back() + 1;
+            newTempSize = (bigint)m_stack.back() + 1;
 			break;
 		case Instruction::MLOAD:
 			require(1);
-			newTempSize = m_stack.back() + 32;
+            newTempSize = (bigint)m_stack.back() + 32;
 			break;
 		case Instruction::RETURN:
 			require(2);
@@ -236,9 +236,9 @@ template <class Ext> dev::bytesConstRef dev::eth::VM::go(Ext& _ext, OnOpFunc con
 		case Instruction::CREATE:
 		{
 			require(3);
-			auto inOff = m_stack[m_stack.size() - 2];
-			auto inSize = m_stack[m_stack.size() - 3];
-			newTempSize = inOff + inSize;
+            u256 inOff = m_stack[m_stack.size() - 2];
+            u256 inSize = m_stack[m_stack.size() - 3];
+            newTempSize = (bigint)inOff + inSize;
             runGas = c_createGas;
 			break;
 		}