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Fix negative denominator in boost::rational during exponentiation. #5348

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Nov 8, 2018
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Fix negative denominator in boost::rational during exponentiation. #5348

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4 changes: 2 additions & 2 deletions libsolidity/ast/Types.cpp
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Expand Up @@ -1144,10 +1144,10 @@ TypePointer RationalNumberType::binaryOperatorResult(Token _operator, TypePointe
bigint denominator = optimizedPow(m_value.denominator(), absExp);

if (exp >= 0)
value = rational(numerator, denominator);
value = makeRational(numerator, denominator);
else
// invert
value = rational(denominator, numerator);
value = makeRational(denominator, numerator);
}
break;
}
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9 changes: 9 additions & 0 deletions libsolidity/ast/Types.h
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Expand Up @@ -51,6 +51,15 @@ using FunctionTypePointer = std::shared_ptr<FunctionType const>;
using TypePointers = std::vector<TypePointer>;
using rational = boost::rational<dev::bigint>;

inline rational makeRational(bigint const& _numerator, bigint const& _denominator)
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I think this would be better suited in an anonymous namespace inside the cpp file or in a more central place inside libdevcore.

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Actually, I don't think so - in this header we introduce the rational alias and - if we want to stay compatible with the buggy boost version - we will always want to use makeRational, when we create a rational from a numerator and denominator, so I think it makes a lot of sense to have it right here below the using rational = ......

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Or if we want to move it, I'd at least move the using rational = ... part as well.

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Cleanly moving using rational = ... to libdevcore would require changing it's namespace, though - which we could do, but which may have side-effects. So actually I think right here is not too bad of a place for this for now :-).

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Ok!

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I think Types.h would need some cleanup at some point anyway....

{
solAssert(_denominator != 0, "division by zero");
// due to a bug in certain versions of boost the denominator has to be positive
if (_denominator < 0)
return rational(-_numerator, -_denominator);
else
return rational(_numerator, _denominator);
}

enum class DataLocation { Storage, CallData, Memory };

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5 changes: 5 additions & 0 deletions test/libsolidity/syntaxTests/types/rational_negative_numerator_negative_exp.sol
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@@ -0,0 +1,5 @@
contract C {
function f() public pure returns (int) {
return (-1 / 2) ** -1;
}
}