Add markAsInvalid to the various assemblies.

libevmasm/Assembly.cpp

@@ -521,6 +521,7 @@ map<u256, u256> Assembly::optimiseInternal(
 
 LinkerObject const& Assembly::assemble() const
 {
+	assertThrow(!m_invalid, AssemblyException, "Attempted to assemble invalid Assembly object.");
 	// Return the already assembled object, if present.
 	if (!m_assembledObject.bytecode.empty())
 		return m_assembledObject;

libevmasm/Assembly.h

@@ -142,6 +142,9 @@ public:
 		std::map<std::string, unsigned> const& _sourceIndices = std::map<std::string, unsigned>()
 	) const;
 
+	/// Mark this assembly as invalid. Calling ``assemble`` on it will throw.
+	void markAsInvalid() { m_invalid = true; }
+
 protected:
 	/// Does the same operations as @a optimise, but should only be applied to a sub and
 	/// returns the replaced tags. Also takes an argument containing the tags of this assembly
@@ -161,6 +164,7 @@ private:
 	);
 	static std::string toStringInHex(u256 _value);
 
+	bool m_invalid = false;
 protected:
 	/// 0 is reserved for exception
 	unsigned m_usedTags = 1;

libyul/backends/evm/AbstractAssembly.h

@@ -111,6 +111,9 @@ public:
 	virtual void appendImmutable(std::string const& _identifier) = 0;
 	/// Appends an assignment to an immutable variable.
 	virtual void appendImmutableAssignment(std::string const& _identifier) = 0;
+
+	/// Mark this assembly as invalid. Any attempt to request bytecode from it should throw.
+	virtual void markAsInvalid() = 0;
 };
 
 enum class IdentifierContext { LValue, RValue, VariableDeclaration };

libyul/backends/evm/AsmCodeGen.cpp

@@ -182,6 +182,11 @@ void EthAssemblyAdapter::appendImmutableAssignment(std::string const& _identifie
 	m_assembly.appendImmutableAssignment(_identifier);
 }
 
+void EthAssemblyAdapter::markAsInvalid()
+{
+	m_assembly.markAsInvalid();
+}
+
 EthAssemblyAdapter::LabelID EthAssemblyAdapter::assemblyTagToIdentifier(evmasm::AssemblyItem const& _tag)
 {
 	u256 id = _tag.data();

libyul/backends/evm/AsmCodeGen.h

@@ -64,6 +64,8 @@ public:
 	void appendImmutable(std::string const& _identifier) override;
 	void appendImmutableAssignment(std::string const& _identifier) override;
 
+	void markAsInvalid() override;
+
 private:
 	static LabelID assemblyTagToIdentifier(evmasm::AssemblyItem const& _tag);
 	void appendJumpInstruction(evmasm::Instruction _instruction, JumpType _jumpType);

libyul/backends/evm/EVMAssembly.cpp

@@ -156,6 +156,7 @@ void EVMAssembly::appendReturnsub(int _returns, int _stackDiffAfter)
 
 evmasm::LinkerObject EVMAssembly::finalize()
 {
+	yulAssert(!m_invalid, "Attempted to finalize invalid assembly object.");
 	size_t bytecodeSize = m_bytecode.size();
 	for (auto const& ref: m_assemblySizePositions)
 		updateReference(ref, assemblySizeReferenceSize, u256(bytecodeSize));

libyul/backends/evm/EVMAssembly.h

@@ -86,6 +86,8 @@ public:
 	void appendImmutable(std::string const& _identifier) override;
 	void appendImmutableAssignment(std::string const& _identifier) override;
 
+	void markAsInvalid() override { m_invalid = true; }
+
 	/// Resolves references inside the bytecode and returns the linker object.
 	evmasm::LinkerObject finalize();
 
@@ -102,6 +104,7 @@ private:
 	std::map<LabelID, size_t> m_labelPositions;
 	std::map<size_t, LabelID> m_labelReferences;
 	std::vector<size_t> m_assemblySizePositions;
+	bool m_invalid = false;
 };
 
 }

libyul/backends/evm/EVMCodeTransform.cpp

@@ -237,6 +237,7 @@ void CodeTransform::stackError(StackTooDeepError _error, int _targetStackHeight)
 		m_assembly.appendConstant(u256(0));
 	// Store error.
 	m_stackErrors.emplace_back(std::move(_error));
+	m_assembly.markAsInvalid();
 }
 
 void CodeTransform::operator()(Assignment const& _assignment)
@@ -448,11 +449,15 @@ void CodeTransform::operator()(FunctionDefinition const& _function)
 		m_context
 	);
 	subTransform(_function.body);
-	for (auto& stackError: subTransform.m_stackErrors)
+	if (!subTransform.m_stackErrors.empty())
 	{
-		if (stackError.functionName.empty())
-			stackError.functionName = _function.name;
-		m_stackErrors.emplace_back(std::move(stackError));
+		m_assembly.markAsInvalid();
+		for (StackTooDeepError& stackError: subTransform.m_stackErrors)
+		{
+			if (stackError.functionName.empty())
+				stackError.functionName = _function.name;
+			m_stackErrors.emplace_back(std::move(stackError));
+		}
 	}
 
 	m_assembly.appendLabel(m_context->functionExitPoints.top().label);
@@ -718,7 +723,7 @@ size_t CodeTransform::variableHeightDiff(Scope::Variable const& _var, YulString
 			to_string(heightDiff - limit) +
 			" slot(s) too deep inside the stack."
 		);
-		// TODO: maybe make this return something special that results in producing INVALID instead.
+		m_assembly.markAsInvalid();
 		return _forSwap ? 2 : 1;
 	}
 	return heightDiff;

libyul/backends/evm/NoOutputAssembly.h

@@ -74,6 +74,8 @@ public:
 	void appendImmutable(std::string const& _identifier) override;
 	void appendImmutableAssignment(std::string const& _identifier) override;
 
+	void markAsInvalid() override {}
+
 private:
 	bool m_evm15 = false; ///< if true, switch to evm1.5 mode
 	int m_stackHeight = 0;