Merge pull request #7161 from ethereum/permit-zerolength-dyn-array-dimensions

Dynamically sized array dimensions can be zero sized

Author: bshastry

test/tools/ossfuzz/protoToAbiV2.cpp

@@ -328,13 +328,10 @@ void ProtoConverter::visit(StructType const&)
 
 std::string ProtoConverter::arrayDimInfoAsString(ArrayDimensionInfo const& _x)
 {
-	unsigned arrLength = getArrayLengthFromFuzz(_x.length());
-	if (_x.is_static())
-		return Whiskers(R"([<length>])")
-		("length", std::to_string(arrLength))
+	return Whiskers(R"([<?isStatic><length></isStatic>])")
+		("isStatic", _x.is_static())
+		("length", std::to_string(getStaticArrayLengthFromFuzz(_x.length())))
 		.render();
-	else
-		return R"([])";
 }
 
 void ProtoConverter::arrayDimensionsAsStringVector(
@@ -398,7 +395,7 @@ ProtoConverter::DataType ProtoConverter::getDataTypeByBaseType(ArrayType const&
 // Adds a resize operation for a given dimension of type `_type` and expression referenced
 // by `_var`. `_isStatic` is true for statically sized dimensions, false otherwise.
 // `_arrayLen` is equal to length of statically sized array dimension. For dynamically
-// sized dimension, we use `getArrayLengthFromFuzz()` and a monotonically increasing
+// sized dimension, we use `getDynArrayLengthFromFuzz()` and a monotonically increasing
 // counter to obtain actual length. Function returns dimension length.
 unsigned ProtoConverter::resizeDimension(
 	bool _isStatic,
@@ -413,7 +410,7 @@ unsigned ProtoConverter::resizeDimension(
 		length = _arrayLen;
 	else
 	{
-		length = getArrayLengthFromFuzz(_arrayLen, getNextCounter());
+		length = getDynArrayLengthFromFuzz(_arrayLen, getNextCounter());
 
 		// If local var, new T(l);
 		// Else, l;

test/tools/ossfuzz/protoToAbiV2.h

@@ -334,14 +334,28 @@ class ProtoConverter
 		return toHex(maskUnsignedInt(_counter, _numMaskNibbles), HexPrefix::Add);
 	}
 
-	static unsigned getArrayLengthFromFuzz(unsigned _fuzz, unsigned _counter = 0)
+	/// Dynamically sized arrays can have a length of at least zero
+	/// and at most s_maxArrayLength.
+	static unsigned getDynArrayLengthFromFuzz(unsigned _fuzz, unsigned _counter)
 	{
-		return ((_fuzz + _counter) % s_maxArrayLength) + 1;
+		// Increment modulo value by one in order to meet upper bound
+		return (_fuzz + _counter) % (s_maxArrayLength + 1);
+	}
+
+	/// Statically sized arrays must have a length of at least one
+	/// and at most s_maxArrayLength.
+	static unsigned getStaticArrayLengthFromFuzz(unsigned _fuzz)
+	{
+		return _fuzz % s_maxArrayLength + 1;
 	}
 
 	static std::pair<bool, unsigned> arrayDimInfoAsPair(ArrayDimensionInfo const& _x)
 	{
-		return std::make_pair(_x.is_static(), getArrayLengthFromFuzz(_x.length()));
+		return (
+			_x.is_static() ?
+			std::make_pair(true, getStaticArrayLengthFromFuzz(_x.length())) :
+			std::make_pair(false, getDynArrayLengthFromFuzz(_x.length(), 0))
+		);
 	}
 
 	/// Contains the test program
@@ -360,7 +374,7 @@ class ProtoConverter
 	unsigned m_varCounter;
 	/// Monotonically increasing return value for error reporting
 	unsigned m_returnValue;
-	static unsigned constexpr s_maxArrayLength = 2;
+	static unsigned constexpr s_maxArrayLength = 4;
 	static unsigned constexpr s_maxArrayDimensions = 10;
 	/// Prefixes for declared and parameterized variable names
 	static auto constexpr s_varNamePrefix = "x_";