path: root/libsolidity/formal/SMTChecker.cpp

/*
    This file is part of solidity.

    solidity is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    solidity is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with solidity.  If not, see <http://www.gnu.org/licenses/>.
*/

#include <libsolidity/formal/SMTChecker.h>

#ifdef HAVE_Z3
#include <libsolidity/formal/Z3Interface.h>
#else
#include <libsolidity/formal/SMTLib2Interface.h>
#endif

#include <libsolidity/interface/ErrorReporter.h>

#include <boost/range/adaptor/map.hpp>

using namespace std;
using namespace dev;
using namespace dev::solidity;

SMTChecker::SMTChecker(ErrorReporter& _errorReporter, ReadCallback::Callback const& _readFileCallback):
#ifdef HAVE_Z3
    m_interface(make_shared<smt::Z3Interface>()),
#else
    m_interface(make_shared<smt::SMTLib2Interface>(_readFileCallback)),
#endif
    m_errorReporter(_errorReporter)
{
    (void)_readFileCallback;
}

void SMTChecker::analyze(SourceUnit const& _source)
{
    if (_source.annotation().experimentalFeatures.count(ExperimentalFeature::SMTChecker))
    {
        m_interface->reset();
        m_currentSequenceCounter.clear();
        m_nextFreeSequenceCounter.clear();
        _source.accept(*this);
    }
}

void SMTChecker::endVisit(VariableDeclaration const& _varDecl)
{
    if (_varDecl.value())
    {
        m_errorReporter.warning(
            _varDecl.location(),
            "Assertion checker does not yet support this."
        );
    }
    else if (_varDecl.isLocalOrReturn())
        createVariable(_varDecl, true);
    else if (_varDecl.isCallableParameter())
        createVariable(_varDecl, false);
}

bool SMTChecker::visit(FunctionDefinition const& _function)
{
    if (!_function.modifiers().empty() || _function.isConstructor())
        m_errorReporter.warning(
            _function.location(),
            "Assertion checker does not yet support constructors and functions with modifiers."
        );
    // TODO actually we probably also have to reset all local variables and similar things.
    m_currentFunction = &_function;
    m_interface->push();
    return true;
}

void SMTChecker::endVisit(FunctionDefinition const&)
{
    // TOOD we could check for "reachability", i.e. satisfiability here.
    // We only handle local variables, so we clear everything.
    // If we add storage variables, those should be cleared differently.
    m_currentSequenceCounter.clear();
    m_nextFreeSequenceCounter.clear();
    m_interface->pop();
    m_currentFunction = nullptr;
}

bool SMTChecker::visit(IfStatement const& _node)
{
    _node.condition().accept(*this);

    // TODO Check if condition is always true

    auto countersAtStart = m_currentSequenceCounter;
    m_interface->push();
    m_interface->addAssertion(expr(_node.condition()));
    _node.trueStatement().accept(*this);
    auto countersAtEndOfTrue = m_currentSequenceCounter;
    m_interface->pop();

    decltype(m_currentSequenceCounter) countersAtEndOfFalse;
    if (_node.falseStatement())
    {
        m_currentSequenceCounter = countersAtStart;
        m_interface->push();
        m_interface->addAssertion(!expr(_node.condition()));
        _node.falseStatement()->accept(*this);
        countersAtEndOfFalse = m_currentSequenceCounter;
        m_interface->pop();
    }
    else
        countersAtEndOfFalse = countersAtStart;

    // Reset all values that have been touched.

    // TODO this should use a previously generated side-effect structure

    solAssert(countersAtEndOfFalse.size() == countersAtEndOfTrue.size(), "");
    for (auto const& declCounter: countersAtEndOfTrue)
    {
        solAssert(countersAtEndOfFalse.count(declCounter.first), "");
        auto decl = declCounter.first;
        int trueCounter = countersAtEndOfTrue.at(decl);
        int falseCounter = countersAtEndOfFalse.at(decl);
        if (trueCounter == falseCounter)
            continue; // Was not modified
        newValue(*decl);
        setValue(*decl, 0);
    }
    return false;
}

bool SMTChecker::visit(WhileStatement const& _node)
{
    _node.condition().accept(*this);

    //m_interface->push();
    //m_interface->addAssertion(expr(_node.condition()));
    // TDOO clear knowledge (increment sequence numbers and add bounds assertions   ) apart from assertions

    // TODO combine similar to if
    return true;
}

void SMTChecker::endVisit(VariableDeclarationStatement const& _varDecl)
{
    if (_varDecl.declarations().size() != 1)
        m_errorReporter.warning(
            _varDecl.location(),
            "Assertion checker does not yet support such variable declarations."
        );
    else if (knownVariable(*_varDecl.declarations()[0]))
    {
        if (_varDecl.initialValue())
            // TODO more checks?
            // TODO add restrictions about type (might be assignment from smaller type)
            m_interface->addAssertion(newValue(*_varDecl.declarations()[0]) == expr(*_varDecl.initialValue()));
    }
    else
        m_errorReporter.warning(
            _varDecl.location(),
            "Assertion checker does not yet implement such variable declarations."
        );
}

void SMTChecker::endVisit(ExpressionStatement const&)
{
}

void SMTChecker::endVisit(Assignment const& _assignment)
{
    if (_assignment.assignmentOperator() != Token::Value::Assign)
        m_errorReporter.warning(
            _assignment.location(),
            "Assertion checker does not yet implement compound assignment."
        );
    else if (_assignment.annotation().type->category() != Type::Category::Integer)
        m_errorReporter.warning(
            _assignment.location(),
            "Assertion checker does not yet implement type " + _assignment.annotation().type->toString()
        );
    else if (Identifier const* identifier = dynamic_cast<Identifier const*>(&_assignment.leftHandSide()))
    {
        Declaration const* decl = identifier->annotation().referencedDeclaration;
        if (knownVariable(*decl))
            // TODO more checks?
            // TODO add restrictions about type (might be assignment from smaller type)
            m_interface->addAssertion(newValue(*decl) == expr(_assignment.rightHandSide()));
        else
            m_errorReporter.warning(
                _assignment.location(),
                "Assertion checker does not yet implement such assignments."
            );
    }
    else
        m_errorReporter.warning(
            _assignment.location(),
            "Assertion checker does not yet implement such assignments."
        );
}

void SMTChecker::endVisit(TupleExpression const& _tuple)
{
    if (_tuple.isInlineArray() || _tuple.components().size() != 1)
        m_errorReporter.warning(
            _tuple.location(),
            "Assertion checker does not yet implement tules and inline arrays."
        );
    else
        m_interface->addAssertion(expr(_tuple) == expr(*_tuple.components()[0]));
}

void SMTChecker::endVisit(BinaryOperation const& _op)
{
    if (Token::isArithmeticOp(_op.getOperator()))
        arithmeticOperation(_op);
    else if (Token::isCompareOp(_op.getOperator()))
        compareOperation(_op);
    else if (Token::isBooleanOp(_op.getOperator()))
        booleanOperation(_op);
    else
        m_errorReporter.warning(
            _op.location(),
            "Assertion checker does not yet implement this operator."
        );
}

void SMTChecker::endVisit(FunctionCall const& _funCall)
{
    FunctionType const& funType = dynamic_cast<FunctionType const&>(*_funCall.expression().annotation().type);

    std::vector<ASTPointer<Expression const>> const args = _funCall.arguments();
    if (funType.kind() == FunctionType::Kind::Assert)
    {
        solAssert(args.size() == 1, "");
        solAssert(args[0]->annotation().type->category() == Type::Category::Bool, "");
        checkCondition(!(expr(*args[0])), _funCall.location(), "Assertion violation");
        m_interface->addAssertion(expr(*args[0]));
    }
    else if (funType.kind() == FunctionType::Kind::Require)
    {
        solAssert(args.size() == 1, "");
        solAssert(args[0]->annotation().type->category() == Type::Category::Bool, "");
        m_interface->addAssertion(expr(*args[0]));
        checkCondition(!(expr(*args[0])), _funCall.location(), "Unreachable code");
        // TODO is there something meaningful we can check here?
        // We can check whether the condition is always fulfilled or never fulfilled.
    }
}

void SMTChecker::endVisit(Identifier const& _identifier)
{
    Declaration const* decl = _identifier.annotation().referencedDeclaration;
    solAssert(decl, "");
    if (dynamic_cast<IntegerType const*>(_identifier.annotation().type.get()))
    {
        m_interface->addAssertion(expr(_identifier) == currentValue(*decl));
        return;
    }
    else if (FunctionType const* fun = dynamic_cast<FunctionType const*>(_identifier.annotation().type.get()))
    {
        if (fun->kind() == FunctionType::Kind::Assert || fun->kind() == FunctionType::Kind::Require)
            return;
        // TODO for others, clear our knowledge about storage and memory
    }
    m_errorReporter.warning(
        _identifier.location(),
        "Assertion checker does not yet support the type of this expression (" +
        _identifier.annotation().type->toString() +
        ")."
    );
}

void SMTChecker::endVisit(Literal const& _literal)
{
    Type const& type = *_literal.annotation().type;
    if (type.category() == Type::Category::Integer || type.category() == Type::Category::RationalNumber)
    {
        if (RationalNumberType const* rational = dynamic_cast<RationalNumberType const*>(&type))
            solAssert(!rational->isFractional(), "");

        m_interface->addAssertion(expr(_literal) == smt::Expression(type.literalValue(&_literal)));
    }
    else
        m_errorReporter.warning(
            _literal.location(),
            "Assertion checker does not yet support the type of this expression (" +
            _literal.annotation().type->toString() +
            ")."
        );
}

void SMTChecker::arithmeticOperation(BinaryOperation const& _op)
{
    switch (_op.getOperator())
    {
    case Token::Add:
    case Token::Sub:
    case Token::Mul:
    {
        solAssert(_op.annotation().commonType, "");
        solAssert(_op.annotation().commonType->category() == Type::Category::Integer, "");
        smt::Expression left(expr(_op.leftExpression()));
        smt::Expression right(expr(_op.rightExpression()));
        Token::Value op = _op.getOperator();
        smt::Expression value(
            op == Token::Add ? left + right :
            op == Token::Sub ? left - right :
            /*op == Token::Mul*/ left * right
        );

        // Overflow check
        auto const& intType = dynamic_cast<IntegerType const&>(*_op.annotation().commonType);
        checkCondition(
            value < minValue(intType),
            _op.location(),
            "Underflow (resulting value less than " + formatNumber(intType.minValue()) + ")",
            "value",
            &value
        );
        checkCondition(
            value > maxValue(intType),
            _op.location(),
            "Overflow (resulting value larger than " + formatNumber(intType.maxValue()) + ")",
            "value",
            &value
        );

        m_interface->addAssertion(expr(_op) == value);
        break;
    }
    default:
        m_errorReporter.warning(
            _op.location(),
            "Assertion checker does not yet implement this operator."
        );
    }
}

void SMTChecker::compareOperation(BinaryOperation const& _op)
{
    solAssert(_op.annotation().commonType, "");
    if (_op.annotation().commonType->category() == Type::Category::Integer)
    {
        smt::Expression left(expr(_op.leftExpression()));
        smt::Expression right(expr(_op.rightExpression()));
        Token::Value op = _op.getOperator();
        smt::Expression value = (
            op == Token::Equal ? (left == right) :
            op == Token::NotEqual ? (left != right) :
            op == Token::LessThan ? (left < right) :
            op == Token::LessThanOrEqual ? (left <= right) :
            op == Token::GreaterThan ? (left > right) :
            /*op == Token::GreaterThanOrEqual*/ (left >= right)
        );
        // TODO: check that other values for op are not possible.
        m_interface->addAssertion(expr(_op) == value);
    }
    else
        m_errorReporter.warning(
            _op.location(),
            "Assertion checker does not yet implement the type " + _op.annotation().commonType->toString() + " for comparisons"
        );
}

void SMTChecker::booleanOperation(BinaryOperation const& _op)
{
    solAssert(_op.getOperator() == Token::And || _op.getOperator() == Token::Or, "");
    solAssert(_op.annotation().commonType, "");
    if (_op.annotation().commonType->category() == Type::Category::Bool)
    {
        if (_op.getOperator() == Token::And)
            m_interface->addAssertion(expr(_op) == expr(_op.leftExpression()) && expr(_op.rightExpression()));
        else
            m_interface->addAssertion(expr(_op) == expr(_op.leftExpression()) || expr(_op.rightExpression()));
    }
    else
        m_errorReporter.warning(
            _op.location(),
            "Assertion checker does not yet implement the type " + _op.annotation().commonType->toString() + " for boolean operations"
        );
}

void SMTChecker::checkCondition(
    smt::Expression _condition,
    SourceLocation const& _location,
    string const& _description,
    string const& _additionalValueName,
    smt::Expression* _additionalValue
)
{
    m_interface->push();
    m_interface->addAssertion(_condition);

    vector<smt::Expression> expressionsToEvaluate;
    vector<string> expressionNames;
    if (m_currentFunction)
    {
        if (_additionalValue)
        {
            expressionsToEvaluate.emplace_back(*_additionalValue);
            expressionNames.push_back(_additionalValueName);
        }
        for (auto const& param: m_currentFunction->parameters())
            if (knownVariable(*param))
            {
                expressionsToEvaluate.emplace_back(currentValue(*param));
                expressionNames.push_back(param->name());
            }
        for (auto const& var: m_currentFunction->localVariables())
            if (knownVariable(*var))
            {
                expressionsToEvaluate.emplace_back(currentValue(*var));
                expressionNames.push_back(var->name());
            }
    }
    smt::CheckResult result;
    vector<string> values;
    try
    {
        tie(result, values) = m_interface->check(expressionsToEvaluate);
    }
    catch (smt::SolverError const& _e)
    {
        string description("Error querying SMT solver");
        if (_e.comment())
            description += ": " + *_e.comment();
        m_errorReporter.warning(_location, description);
        return;
    }

    switch (result)
    {
    case smt::CheckResult::SATISFIABLE:
    {
        std::ostringstream message;
        message << _description << " happens here";
        if (m_currentFunction)
        {
            message << " for:\n";
            solAssert(values.size() == expressionNames.size(), "");
            for (size_t i = 0; i < values.size(); ++i)
            {
                string formattedValue = values.at(i);
                try
                {
                    // Parse and re-format nicely
                    formattedValue = formatNumber(bigint(formattedValue));
                }
                catch (...) { }

                message << "  " << expressionNames.at(i) << " = " << formattedValue << "\n";
            }
        }
        else
            message << ".";
        m_errorReporter.warning(_location, message.str());
        break;
    }
    case smt::CheckResult::UNSATISFIABLE:
        break;
    case smt::CheckResult::UNKNOWN:
        m_errorReporter.warning(_location, _description + " might happen here.");
        break;
    case smt::CheckResult::ERROR:
        m_errorReporter.warning(_location, "Error trying to invoke SMT solver.");
        break;
    default:
        solAssert(false, "");
    }
    m_interface->pop();
}

void SMTChecker::createVariable(VariableDeclaration const& _varDecl, bool _setToZero)
{
    if (dynamic_cast<IntegerType const*>(_varDecl.type().get()))
    {
        solAssert(m_currentSequenceCounter.count(&_varDecl) == 0, "");
        solAssert(m_nextFreeSequenceCounter.count(&_varDecl) == 0, "");
        solAssert(m_Variables.count(&_varDecl) == 0, "");
        m_currentSequenceCounter[&_varDecl] = 0;
        m_nextFreeSequenceCounter[&_varDecl] = 1;
        m_Variables.emplace(&_varDecl, m_interface->newFunction(uniqueSymbol(_varDecl), smt::Sort::Int, smt::Sort::Int));
        setValue(_varDecl, _setToZero);
    }
    else
        m_errorReporter.warning(
            _varDecl.location(),
            "Assertion checker does not yet support the type of this variable."
        );
}

string SMTChecker::uniqueSymbol(Declaration const& _decl)
{
    return _decl.name() + "_" + to_string(_decl.id());
}

string SMTChecker::uniqueSymbol(Expression const& _expr)
{
    return "expr_" + to_string(_expr.id());
}

bool SMTChecker::knownVariable(Declaration const& _decl)
{
    return m_currentSequenceCounter.count(&_decl);
}

smt::Expression SMTChecker::currentValue(Declaration const& _decl)
{
    solAssert(m_currentSequenceCounter.count(&_decl), "");
    return valueAtSequence(_decl, m_currentSequenceCounter.at(&_decl));
}

smt::Expression SMTChecker::valueAtSequence(const Declaration& _decl, int _sequence)
{
    return var(_decl)(_sequence);
}

smt::Expression SMTChecker::newValue(Declaration const& _decl)
{
    solAssert(m_currentSequenceCounter.count(&_decl), "");
    solAssert(m_nextFreeSequenceCounter.count(&_decl), "");
    m_currentSequenceCounter[&_decl] = m_nextFreeSequenceCounter[&_decl]++;
    return currentValue(_decl);
}

void SMTChecker::setValue(Declaration const& _decl, bool _setToZero)
{
    auto const& intType = dynamic_cast<IntegerType const&>(*_decl.type());

    if (_setToZero)
        m_interface->addAssertion(currentValue(_decl) == 0);
    else
    {
        m_interface->addAssertion(currentValue(_decl) >= minValue(intType));
        m_interface->addAssertion(currentValue(_decl) <= maxValue(intType));
    }
}

smt::Expression SMTChecker::minValue(IntegerType const& _t)
{
    return smt::Expression(_t.minValue());
}

smt::Expression SMTChecker::maxValue(IntegerType const& _t)
{
    return smt::Expression(_t.maxValue());
}

smt::Expression SMTChecker::expr(Expression const& _e)
{
    if (!m_Expressions.count(&_e))
    {
        solAssert(_e.annotation().type, "");
        switch (_e.annotation().type->category())
        {
        case Type::Category::RationalNumber:
        {
            if (RationalNumberType const* rational = dynamic_cast<RationalNumberType const*>(_e.annotation().type.get()))
                solAssert(!rational->isFractional(), "");
            m_Expressions.emplace(&_e, m_interface->newInteger(uniqueSymbol(_e)));
            break;
        }
        case Type::Category::Integer:
            m_Expressions.emplace(&_e, m_interface->newInteger(uniqueSymbol(_e)));
            break;
        case Type::Category::Bool:
            m_Expressions.emplace(&_e, m_interface->newBool(uniqueSymbol(_e)));
            break;
        default:
            solAssert(false, "Type not implemented.");
        }
    }
    return m_Expressions.at(&_e);
}

smt::Expression SMTChecker::var(Declaration const& _decl)
{
    solAssert(m_Variables.count(&_decl), "");
    return m_Variables.at(&_decl);
}