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[SMTChecker] Adding division by zero checks in the CHC engine

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This commit is contained in:
Martin Blicha
2020-10-21 14:48:33 +02:00
parent a83ad58109
commit f0d81601db
16 changed files with 126 additions and 145 deletions
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libsolidity/formal/SMTEncoder.cpp
+6 -7
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@@ -787,7 +787,6 @@ void SMTEncoder::visitAddMulMod(FunctionCall const& _funCall)
auto x = expr(*args.at(0));
auto y = expr(*args.at(1));
auto k = expr(*args.at(2));
m_context.addAssertion(k != 0);
auto const& intType = dynamic_cast<IntegerType const&>(*_funCall.annotation().type);
if (kind == FunctionType::Kind::AddMod)
@@ -1532,8 +1531,6 @@ pair<smtutil::Expression, smtutil::Expression> SMTEncoder::arithmeticOperation(
if (_op == Token::Div || _op == Token::Mod)
{
m_context.addAssertion(_right != 0);
// mod and unsigned division never underflow/overflow
if (_op == Token::Mod || !intType->isSigned())
return {valueUnbounded, valueUnbounded};
@@ -1744,13 +1741,15 @@ pair<smtutil::Expression, smtutil::Expression> SMTEncoder::divModWithSlacks(
m_context.addAssertion(((d.currentValue() * _right) + r.currentValue()) == _left);
if (_type.isSigned())
m_context.addAssertion(
(_left >= 0 && 0 <= r.currentValue() && r.currentValue() < smtutil::abs(_right)) ||
(_left < 0 && (0 - smtutil::abs(_right)) < r.currentValue() && r.currentValue() <= 0)
(_left >= 0 && 0 <= r.currentValue() && (_right == 0 || r.currentValue() < smtutil::abs(_right))) ||
(_left < 0 && ((_right == 0 || 0 - smtutil::abs(_right) < r.currentValue()) && r.currentValue() <= 0))
);
else // unsigned version
m_context.addAssertion(0 <= r.currentValue() && r.currentValue() < _right);
m_context.addAssertion(0 <= r.currentValue() && (_right == 0 || r.currentValue() < _right));
return {d.currentValue(), r.currentValue()};
auto divResult = smtutil::Expression::ite(_right == 0, 0, d.currentValue());
auto modResult = smtutil::Expression::ite(_right == 0, 0, r.currentValue());
return {divResult, modResult};
}
void SMTEncoder::assignment(