Implement account existence / emptiness notions.

libethereum/ExtVM.h

@@ -76,7 +76,13 @@ class ExtVM: public ExtVMFace
 	virtual u256 txCount(Address _a) override final { return m_s.transactionsFrom(_a); }
 
 	/// Does the account exist?
-	virtual bool exists(Address _a) override final { return m_s.addressInUse(_a); }
+	virtual bool exists(Address _a) override final
+	{
+		if (evmSchedule().emptinessIsNonexistence())
+			return m_s.accountNonemptyOrExisting(_a);
+		else
+			return m_s.addressInUse(_a);
+	}
 
 	/// Suicide the associated contract to the given address.
 	virtual void suicide(Address _a) override final

libethereum/State.h

@@ -159,6 +159,10 @@ class State
 	/// Check if the address is in use.
 	bool addressInUse(Address const& _address) const;
 
+	/// Check if the account does not exist in the state or is empty (nonce == 0, balance == 0, code empty).
+	/// These two notions are equivalent after EIP158.
+	bool accountNonemptyOrExisting(Address const& _address) const;
+
 	/// Check if the address contains executable code.
 	bool addressHasCode(Address const& _address) const;
 

libevmcore/EVMSchedule.h

@@ -36,6 +36,7 @@ struct EVMSchedule
 	bool exceptionalFailedCodeDeposit = true;
 	bool haveDelegateCall = true;
 	bool eip150Mode = false;
+	bool eip158Mode = false;
 	unsigned stackLimit = 1024;
 	std::array<unsigned, 8> tierStepGas;
 	unsigned expGas = 10;
@@ -72,6 +73,7 @@ struct EVMSchedule
 
 	bool staticCallDepthLimit() const { return !eip150Mode; }
 	bool suicideChargesNewAccountGas() const { return eip150Mode; }
+	bool emptinessIsNonexistence() const { return eip158Mode; }
 };
 
 static const EVMSchedule DefaultSchedule = EVMSchedule();
@@ -95,6 +97,7 @@ static const EVMSchedule EIP158Schedule = []
 {
 	EVMSchedule schedule = EIP150Schedule;
 	schedule.expByteGas = 50;
+	schedule.eip158Mode = true;
 	return schedule;
 }();