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https://github.com/ethereum/solidity
synced 2023-10-03 13:03:40 +00:00
[SMTChecker] Variables are merged after branches (ite variables)
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@ -91,15 +91,16 @@ bool SMTChecker::visit(IfStatement const& _node)
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checkBooleanNotConstant(_node.condition(), "Condition is always $VALUE.");
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checkBooleanNotConstant(_node.condition(), "Condition is always $VALUE.");
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visitBranch(_node.trueStatement(), expr(_node.condition()));
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auto countersEndFalse = m_currentSequenceCounter;
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auto countersEndTrue = visitBranch(_node.trueStatement(), expr(_node.condition()));
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vector<Declaration const*> touchedVariables = m_variableUsage->touchedVariables(_node.trueStatement());
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vector<Declaration const*> touchedVariables = m_variableUsage->touchedVariables(_node.trueStatement());
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if (_node.falseStatement())
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if (_node.falseStatement())
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{
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{
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visitBranch(*_node.falseStatement(), !expr(_node.condition()));
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countersEndFalse = visitBranch(*_node.falseStatement(), !expr(_node.condition()));
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touchedVariables += m_variableUsage->touchedVariables(*_node.falseStatement());
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touchedVariables += m_variableUsage->touchedVariables(*_node.falseStatement());
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}
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}
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resetVariables(touchedVariables);
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mergeVariables(touchedVariables, expr(_node.condition()), countersEndTrue, countersEndFalse);
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return false;
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return false;
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}
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}
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@ -506,12 +507,12 @@ void SMTChecker::assignment(Declaration const& _variable, smt::Expression const&
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m_interface->addAssertion(newValue(_variable) == _value);
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m_interface->addAssertion(newValue(_variable) == _value);
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}
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}
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void SMTChecker::visitBranch(Statement const& _statement, smt::Expression _condition)
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SMTChecker::VariableSequenceCounters SMTChecker::visitBranch(Statement const& _statement, smt::Expression _condition)
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{
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{
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visitBranch(_statement, &_condition);
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return visitBranch(_statement, &_condition);
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}
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}
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void SMTChecker::visitBranch(Statement const& _statement, smt::Expression const* _condition)
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SMTChecker::VariableSequenceCounters SMTChecker::visitBranch(Statement const& _statement, smt::Expression const* _condition)
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{
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{
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VariableSequenceCounters sequenceCountersStart = m_currentSequenceCounter;
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VariableSequenceCounters sequenceCountersStart = m_currentSequenceCounter;
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@ -522,7 +523,8 @@ void SMTChecker::visitBranch(Statement const& _statement, smt::Expression const*
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popPathCondition();
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popPathCondition();
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m_conditionalExecutionHappened = true;
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m_conditionalExecutionHappened = true;
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m_currentSequenceCounter = sequenceCountersStart;
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std::swap(sequenceCountersStart, m_currentSequenceCounter);
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return sequenceCountersStart;
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}
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}
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void SMTChecker::checkCondition(
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void SMTChecker::checkCondition(
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@ -702,6 +704,22 @@ void SMTChecker::resetVariables(vector<Declaration const*> _variables)
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}
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}
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}
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}
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void SMTChecker::mergeVariables(vector<Declaration const*> const& _variables, smt::Expression const& _condition, VariableSequenceCounters const& _countersEndTrue, VariableSequenceCounters const& _countersEndFalse)
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{
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set<Declaration const*> uniqueVars(_variables.begin(), _variables.end());
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for (auto const* decl: uniqueVars)
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{
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int trueCounter = _countersEndTrue.at(decl);
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int falseCounter = _countersEndFalse.at(decl);
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solAssert(trueCounter != falseCounter, "");
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m_interface->addAssertion(newValue(*decl) == smt::Expression::ite(
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_condition,
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valueAtSequence(*decl, trueCounter),
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valueAtSequence(*decl, falseCounter))
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);
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}
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}
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bool SMTChecker::createVariable(VariableDeclaration const& _varDecl)
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bool SMTChecker::createVariable(VariableDeclaration const& _varDecl)
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{
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{
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if (dynamic_cast<IntegerType const*>(_varDecl.type().get()))
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if (dynamic_cast<IntegerType const*>(_varDecl.type().get()))
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@ -75,10 +75,14 @@ private:
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void assignment(Declaration const& _variable, Expression const& _value, SourceLocation const& _location);
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void assignment(Declaration const& _variable, Expression const& _value, SourceLocation const& _location);
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void assignment(Declaration const& _variable, smt::Expression const& _value, SourceLocation const& _location);
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void assignment(Declaration const& _variable, smt::Expression const& _value, SourceLocation const& _location);
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// Visits the branch given by the statement, pushes and pops the SMT checker.
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/// Maps a variable to an SSA index.
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// @param _condition if present, asserts that this condition is true within the branch.
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using VariableSequenceCounters = std::map<Declaration const*, int>;
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void visitBranch(Statement const& _statement, smt::Expression const* _condition = nullptr);
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void visitBranch(Statement const& _statement, smt::Expression _condition);
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/// Visits the branch given by the statement, pushes and pops the current path conditions.
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/// @param _condition if present, asserts that this condition is true within the branch.
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/// @returns the variable sequence counter after visiting the branch.
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VariableSequenceCounters visitBranch(Statement const& _statement, smt::Expression const* _condition = nullptr);
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VariableSequenceCounters visitBranch(Statement const& _statement, smt::Expression _condition);
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/// Check that a condition can be satisfied.
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/// Check that a condition can be satisfied.
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void checkCondition(
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void checkCondition(
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@ -106,6 +110,10 @@ private:
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void initializeLocalVariables(FunctionDefinition const& _function);
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void initializeLocalVariables(FunctionDefinition const& _function);
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void resetVariables(std::vector<Declaration const*> _variables);
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void resetVariables(std::vector<Declaration const*> _variables);
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/// Given two different branches and the touched variables,
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/// merge the touched variables into after-branch ite variables
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/// using the branch condition as guard.
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void mergeVariables(std::vector<Declaration const*> const& _variables, smt::Expression const& _condition, VariableSequenceCounters const& _countersEndTrue, VariableSequenceCounters const& _countersEndFalse);
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/// Tries to create an uninitialized variable and returns true on success.
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/// Tries to create an uninitialized variable and returns true on success.
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/// This fails if the type is not supported.
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/// This fails if the type is not supported.
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bool createVariable(VariableDeclaration const& _varDecl);
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bool createVariable(VariableDeclaration const& _varDecl);
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@ -134,8 +142,6 @@ private:
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static smt::Expression minValue(IntegerType const& _t);
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static smt::Expression minValue(IntegerType const& _t);
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static smt::Expression maxValue(IntegerType const& _t);
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static smt::Expression maxValue(IntegerType const& _t);
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using VariableSequenceCounters = std::map<Declaration const*, int>;
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/// Returns the expression corresponding to the AST node. Throws if the expression does not exist.
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/// Returns the expression corresponding to the AST node. Throws if the expression does not exist.
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smt::Expression expr(Expression const& _e);
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smt::Expression expr(Expression const& _e);
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/// Creates the expression (value can be arbitrary)
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/// Creates the expression (value can be arbitrary)
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@ -168,9 +168,9 @@ BOOST_AUTO_TEST_CASE(function_call_does_not_clear_local_vars)
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CHECK_SUCCESS_NO_WARNINGS(text);
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CHECK_SUCCESS_NO_WARNINGS(text);
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}
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}
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BOOST_AUTO_TEST_CASE(branches_clear_variables)
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BOOST_AUTO_TEST_CASE(branches_merge_variables)
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{
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{
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// Only clears accessed variables
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// Branch does not touch variable a
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string text = R"(
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string text = R"(
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contract C {
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contract C {
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function f(uint x) public pure {
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function f(uint x) public pure {
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@ -182,7 +182,7 @@ BOOST_AUTO_TEST_CASE(branches_clear_variables)
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}
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}
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)";
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)";
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CHECK_SUCCESS_NO_WARNINGS(text);
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CHECK_SUCCESS_NO_WARNINGS(text);
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// It is just a plain clear and will not combine branches.
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// Positive branch touches variable a, but assertion should still hold.
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text = R"(
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text = R"(
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contract C {
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contract C {
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function f(uint x) public pure {
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function f(uint x) public pure {
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@ -194,8 +194,8 @@ BOOST_AUTO_TEST_CASE(branches_clear_variables)
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}
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}
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}
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}
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)";
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)";
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CHECK_WARNING(text, "Assertion violation happens here");
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CHECK_SUCCESS_NO_WARNINGS(text);
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// Clear also works on the else branch
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// Negative branch touches variable a, but assertion should still hold.
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text = R"(
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text = R"(
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contract C {
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contract C {
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function f(uint x) public pure {
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function f(uint x) public pure {
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@ -208,8 +208,8 @@ BOOST_AUTO_TEST_CASE(branches_clear_variables)
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}
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}
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}
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}
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)";
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)";
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CHECK_WARNING(text, "Assertion violation happens here");
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CHECK_SUCCESS_NO_WARNINGS(text);
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// Variable is not cleared, if it is only read.
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// Variable is not merged, if it is only read.
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text = R"(
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text = R"(
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contract C {
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contract C {
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function f(uint x) public pure {
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function f(uint x) public pure {
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@ -224,6 +224,36 @@ BOOST_AUTO_TEST_CASE(branches_clear_variables)
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}
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}
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)";
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)";
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CHECK_SUCCESS_NO_WARNINGS(text);
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CHECK_SUCCESS_NO_WARNINGS(text);
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// Variable is reset in both branches
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text = R"(
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contract C {
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function f(uint x) public pure {
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uint a = 2;
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if (x > 10) {
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a = 3;
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} else {
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a = 3;
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}
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assert(a == 3);
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}
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}
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)";
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CHECK_SUCCESS_NO_WARNINGS(text);
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// Variable is reset in both branches
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text = R"(
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contract C {
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function f(uint x) public pure {
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uint a = 2;
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if (x > 10) {
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a = 3;
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} else {
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a = 4;
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}
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assert(a >= 3);
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}
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}
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)";
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CHECK_SUCCESS_NO_WARNINGS(text);
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}
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}
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BOOST_AUTO_TEST_CASE(branches_assert_condition)
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BOOST_AUTO_TEST_CASE(branches_assert_condition)
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@ -262,7 +292,7 @@ BOOST_AUTO_TEST_CASE(branches_assert_condition)
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CHECK_SUCCESS_NO_WARNINGS(text);
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CHECK_SUCCESS_NO_WARNINGS(text);
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}
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}
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BOOST_AUTO_TEST_CASE(ways_to_clear_variables)
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BOOST_AUTO_TEST_CASE(ways_to_merge_variables)
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{
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{
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string text = R"(
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string text = R"(
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contract C {
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contract C {
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@ -275,6 +305,7 @@ BOOST_AUTO_TEST_CASE(ways_to_clear_variables)
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}
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}
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}
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}
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)";
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)";
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CHECK_WARNING(text, "Assertion violation happens here");
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text = R"(
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text = R"(
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contract C {
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contract C {
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function f(uint x) public pure {
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function f(uint x) public pure {
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