Refactor state as tuple

libsolidity/formal/SymbolicState.cpp

@@ -16,24 +16,42 @@
 */
 // SPDX-License-Identifier: GPL-3.0
 
+#include "libsmtutil/SolverInterface.h"
 #include <libsolidity/formal/SymbolicState.h>
 
+#include <libsolidity/formal/SymbolicTypes.h>
 #include <libsolidity/formal/EncodingContext.h>
 
 using namespace std;
 using namespace solidity;
+using namespace solidity::smtutil;
 using namespace solidity::frontend::smt;
 
 SymbolicState::SymbolicState(EncodingContext& _context):
 	m_context(_context)
 {
+	m_stateMembers.emplace("balances", make_shared<smtutil::ArraySort>(smtutil::SortProvider::uintSort, smtutil::SortProvider::uintSort));
+
+	vector<string> members;
+	vector<SortPointer> sorts;
+	for (auto const& [component, sort]: m_stateMembers)
+	{
+		members.emplace_back(component);
+		sorts.emplace_back(sort);
+		m_componentIndices[component] = members.size() - 1;
+	}
+	m_stateTuple = make_unique<SymbolicTupleVariable>(
+		make_shared<smtutil::TupleSort>("state_type", members, sorts),
+		"state",
+		m_context
+	);
 }
 
 void SymbolicState::reset()
 {
-	m_thisAddress.resetIndex();
-	m_balances.resetIndex();
 	m_error.resetIndex();
+	m_thisAddress.resetIndex();
+	m_stateTuple->resetIndex();
 }
 
 // Blockchain
@@ -43,14 +61,19 @@ smtutil::Expression SymbolicState::thisAddress()
 	return m_thisAddress.currentValue();
 }
 
+smtutil::Expression SymbolicState::balances()
+{
+	return m_stateTuple->component(m_componentIndices.at("balances"));
+}
+
 smtutil::Expression SymbolicState::balance()
 {
-	return balance(m_thisAddress.currentValue());
+	return balance(thisAddress());
 }
 
 smtutil::Expression SymbolicState::balance(smtutil::Expression _address)
 {
-	return smtutil::Expression::select(m_balances.elements(), move(_address));
+	return smtutil::Expression::select(balances(), move(_address));
 }
 
 SymbolicIntVariable& SymbolicState::errorFlag()
@@ -58,21 +81,31 @@ SymbolicIntVariable& SymbolicState::errorFlag()
 	return m_error;
 }
 
+smtutil::Expression SymbolicState::state()
+{
+	return m_stateTuple->currentValue();
+}
+
+SortPointer SymbolicState::stateSort()
+{
+	return m_stateTuple->sort();
+}
+
 void SymbolicState::transfer(smtutil::Expression _from, smtutil::Expression _to, smtutil::Expression _value)
 {
-	unsigned indexBefore = m_balances.index();
+	unsigned indexBefore = m_stateTuple->index();
 	addBalance(_from, 0 - _value);
 	addBalance(_to, move(_value));
-	unsigned indexAfter = m_balances.index();
+	unsigned indexAfter = m_stateTuple->index();
 	solAssert(indexAfter > indexBefore, "");
-	m_balances.increaseIndex();
+	m_stateTuple->increaseIndex();
 	/// Do not apply the transfer operation if _from == _to.
-	auto newBalances = smtutil::Expression::ite(
+	auto newState = smtutil::Expression::ite(
 		move(_from) == move(_to),
-		m_balances.valueAtIndex(indexBefore),
+		m_stateTuple->valueAtIndex(indexBefore),
-		m_balances.valueAtIndex(indexAfter)
+		m_stateTuple->valueAtIndex(indexAfter)
 	);
-	m_context.addAssertion(m_balances.currentValue() == newBalances);
+	m_context.addAssertion(m_stateTuple->currentValue() == newState);
 }
 
 /// Private helpers.
@@ -80,13 +113,24 @@ void SymbolicState::transfer(smtutil::Expression _from, smtutil::Expression _to,
 void SymbolicState::addBalance(smtutil::Expression _address, smtutil::Expression _value)
 {
 	auto newBalances = smtutil::Expression::store(
-		m_balances.elements(),
+		balances(),
 		_address,
 		balance(_address) + move(_value)
 	);
-	auto oldLength = m_balances.length();
+	assignStateMember("balances", newBalances);
-	m_balances.increaseIndex();
-	m_context.addAssertion(m_balances.elements() == newBalances);
-	m_context.addAssertion(m_balances.length() == oldLength);
 }
 
+smtutil::Expression SymbolicState::assignStateMember(string const& _member, smtutil::Expression const& _value)
+{
+	vector<smtutil::Expression> args;
+	for (auto const& member: m_stateMembers)
+		if (member.first == _member)
+			args.emplace_back(_value);
+		else
+			args.emplace_back(m_stateTuple->component(m_componentIndices.at(member.first)));
+	m_stateTuple->increaseIndex();
+	auto tuple = m_stateTuple->currentValue();
+	auto sortExpr = smtutil::Expression(make_shared<smtutil::SortSort>(tuple.sort), tuple.name);
+	m_context.addAssertion(tuple == smtutil::Expression::tuple_constructor(sortExpr, args));
+	return m_stateTuple->currentValue();
+}

libsolidity/formal/SymbolicState.h

@@ -27,9 +27,17 @@ namespace solidity::frontend::smt
 {
 
 class EncodingContext;
+class SymbolicAddressVariable;
+class SymbolicArrayVariable;
 
 /**
- * Symbolic representation of the blockchain state.
+ * Symbolic representation of the blockchain context:
+ * - error flag
+ * - this (the address of the currently executing contract)
+ * - state, represented as a tuple of:
+ *   - balances
+ *   - TODO: potentially storage of contracts
+ * - TODO transaction variables
  */
 class SymbolicState
 {
@@ -42,6 +50,8 @@ public:
 	//@{
 	/// Value of `this` address.
 	smtutil::Expression thisAddress();
+	/// @returns the symbolic balances.
+	smtutil::Expression balances();
 	/// @returns the symbolic balance of address `this`.
 	smtutil::Expression balance();
 	/// @returns the symbolic balance of an address.
@@ -49,6 +59,12 @@ public:
 
 	SymbolicIntVariable& errorFlag();
 
+	/// @returns the state as a tuple.
+	smtutil::Expression state();
+
+	/// @returns the state sort.
+	smtutil::SortPointer stateSort();
+
 	/// Transfer _value from _from to _to.
 	void transfer(smtutil::Expression _from, smtutil::Expression _to, smtutil::Expression _value);
 	//@}
@@ -57,27 +73,27 @@ private:
 	/// Adds _value to _account's balance.
 	void addBalance(smtutil::Expression _account, smtutil::Expression _value);
 
+	/// Generates a new tuple where _member is assigned _value.
+	smtutil::Expression assignStateMember(std::string const& _member, smtutil::Expression const& _value);
+
 	EncodingContext& m_context;
 
-	/// Symbolic `this` address.
+	SymbolicIntVariable m_error{
-	SymbolicAddressVariable m_thisAddress{
-		"this",
-		m_context
-	};
-
-	/// Symbolic balances.
-	SymbolicArrayVariable m_balances{
-		std::make_shared<smtutil::ArraySort>(smtutil::SortProvider::uintSort, smtutil::SortProvider::uintSort),
-		"balances",
-		m_context
-	};
-
-	smt::SymbolicIntVariable m_error{
 		TypeProvider::uint256(),
 		TypeProvider::uint256(),
 		"error",
 		m_context
 	};
+
+	SymbolicAddressVariable m_thisAddress{
+		"this",
+		m_context
+	};
+
+	std::map<std::string, unsigned> m_componentIndices;
+	/// balances, TODO storage of other contracts
+	std::map<std::string, smtutil::SortPointer> m_stateMembers;
+	std::unique_ptr<SymbolicTupleVariable> m_stateTuple;
 };
 
 }