Merge pull request #5923 from ethereum/detectStackProblem

Detect stack problem

libsolidity/codegen/AsmCodeGen.cpp

@@ -184,18 +184,20 @@ void CodeGenerator::assemble(
 )
 {
 	EthAssemblyAdapter assemblyAdapter(_assembly);
+	shared_ptr<EVMDialect> dialect = EVMDialect::strictAssemblyForEVM();
+	CodeTransform transform(
+		assemblyAdapter,
+		_analysisInfo,
+		_parsedData,
+		*dialect,
+		_optimize,
+		false,
+		_identifierAccess,
+		_useNamedLabelsForFunctions
+	);
 	try
 	{
-		CodeTransform(
-			assemblyAdapter,
-			_analysisInfo,
-			_parsedData,
-			*EVMDialect::strictAssemblyForEVM(),
-			_optimize,
-			false,
-			_identifierAccess,
-			_useNamedLabelsForFunctions
-		)(_parsedData);
+		transform(_parsedData);
 	}
 	catch (StackTooDeepError const& _e)
 	{
@@ -205,4 +207,5 @@ void CodeGenerator::assemble(
 				(_e.comment() ? ": " + *_e.comment() : ".")
 			));
 	}
+	solAssert(transform.stackErrors().empty(), "Stack errors present but not thrown.");
 }

libyul/AsmAnalysis.cpp

@@ -55,6 +55,26 @@ bool AsmAnalyzer::analyze(Block const& _block)
 	return (*this)(_block);
 }
 
+AsmAnalysisInfo AsmAnalyzer::analyzeStrictAssertCorrect(
+	shared_ptr<Dialect> _dialect,
+	EVMVersion _evmVersion,
+	Block const& _ast
+)
+{
+	ErrorList errorList;
+	langutil::ErrorReporter errors(errorList);
+	yul::AsmAnalysisInfo analysisInfo;
+	bool success = yul::AsmAnalyzer(
+		analysisInfo,
+		errors,
+		_evmVersion,
+		Error::Type::SyntaxError,
+		_dialect
+	).analyze(_ast);
+	solAssert(success && errorList.empty(), "Invalid assembly/yul code.");
+	return analysisInfo;
+}
+
 bool AsmAnalyzer::operator()(Label const& _label)
 {
 	solAssert(!_label.name.empty(), "");

libyul/AsmAnalysis.h

@@ -72,6 +72,12 @@ public:
 
 	bool analyze(Block const& _block);
 
+	static AsmAnalysisInfo analyzeStrictAssertCorrect(
+		std::shared_ptr<Dialect> _dialect,
+		dev::solidity::EVMVersion _evmVersion,
+		Block const& _ast
+	);
+
 	bool operator()(Instruction const&);
 	bool operator()(Literal const& _literal);
 	bool operator()(Identifier const&);

libyul/CMakeLists.txt

@@ -13,6 +13,8 @@ add_library(yul
 	AsmScope.h
 	AsmScopeFiller.cpp
 	AsmScopeFiller.h
+	CompilabilityChecker.cpp
+	CompilabilityChecker.h
 	Dialect.cpp
 	Dialect.h
 	Exceptions.h
@@ -32,6 +34,8 @@ add_library(yul
 	backends/evm/EVMDialect.h
 	backends/evm/EVMObjectCompiler.cpp
 	backends/evm/EVMObjectCompiler.h
+	backends/evm/NoOutputAssembly.h
+	backends/evm/NoOutputAssembly.cpp
 	optimiser/ASTCopier.cpp
 	optimiser/ASTCopier.h
 	optimiser/ASTWalker.cpp

libyul/CompilabilityChecker.cpp

@@ -0,0 +1,64 @@
+/*(
+	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/>.
+*/
+/**
+ * Component that checks whether all variables are reachable on the stack.
+ */
+
+#include <libyul/CompilabilityChecker.h>
+
+#include <libyul/AsmAnalysis.h>
+#include <libyul/AsmAnalysisInfo.h>
+
+#include <libyul/backends/evm/EVMCodeTransform.h>
+#include <libyul/backends/evm/NoOutputAssembly.h>
+
+#include <liblangutil/EVMVersion.h>
+
+using namespace std;
+using namespace yul;
+using namespace dev;
+using namespace dev::solidity;
+
+std::map<YulString, int> CompilabilityChecker::run(std::shared_ptr<Dialect> _dialect, Block const& _ast)
+{
+	if (_dialect->flavour == AsmFlavour::Yul)
+		return {};
+
+	solAssert(_dialect->flavour == AsmFlavour::Strict, "");
+
+	EVMDialect const& evmDialect = dynamic_cast<EVMDialect const&>(*_dialect);
+
+	bool optimize = true;
+	yul::AsmAnalysisInfo analysisInfo =
+		yul::AsmAnalyzer::analyzeStrictAssertCorrect(_dialect, EVMVersion(), _ast);
+	NoOutputAssembly assembly;
+	CodeTransform transform(assembly, analysisInfo, _ast, evmDialect, optimize);
+	try
+	{
+		transform(_ast);
+	}
+	catch (StackTooDeepError const&)
+	{
+		solAssert(!transform.stackErrors().empty(), "Got stack too deep exception that was not stored.");
+	}
+
+	std::map<YulString, int> functions;
+	for (StackTooDeepError const& error: transform.stackErrors())
+		functions[error.functionName] = max(error.depth, functions[error.functionName]);
+
+	return functions;
+}

libyul/CompilabilityChecker.h

@@ -0,0 +1,45 @@
+/*
+	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/>.
+*/
+/**
+ * Component that checks whether all variables are reachable on the stack.
+ */
+
+#pragma once
+
+#include <libyul/Dialect.h>
+#include <libyul/AsmDataForward.h>
+
+#include <map>
+#include <memory>
+
+namespace yul
+{
+
+/**
+ * Component that checks whether all variables are reachable on the stack and
+ * returns a mapping from function name to the largest stack difference found
+ * in that function (no entry present if that function is compilable).
+ * This only works properly if the outermost block is compilable and
+ * functions are not nested. Otherwise, it might miss reporting some functions.
+ */
+class CompilabilityChecker
+{
+public:
+	static std::map<YulString, int> run(std::shared_ptr<Dialect> _dialect, Block const& _ast);
+};
+
+}

libyul/backends/evm/EVMCodeTransform.cpp

@@ -227,6 +227,18 @@ void CodeTransform::operator()(VariableDeclaration const& _varDecl)
 	checkStackHeight(&_varDecl);
 }
 
+void CodeTransform::stackError(StackTooDeepError _error, int _targetStackHeight)
+{
+	m_assembly.appendInstruction(solidity::Instruction::INVALID);
+	// Correct the stack.
+	while (m_assembly.stackHeight() > _targetStackHeight)
+		m_assembly.appendInstruction(solidity::Instruction::POP);
+	while (m_assembly.stackHeight() < _targetStackHeight)
+		m_assembly.appendConstant(u256(0));
+	// Store error.
+	m_stackErrors.emplace_back(std::move(_error));
+}
+
 void CodeTransform::operator()(Assignment const& _assignment)
 {
 	int height = m_assembly.stackHeight();
@@ -513,18 +525,32 @@ void CodeTransform::operator()(FunctionDefinition const& _function)
 		m_assembly.appendConstant(u256(0));
 	}
 
-	CodeTransform(
-		m_assembly,
-		m_info,
-		_function.body,
-		m_allowStackOpt,
-		m_dialect,
-		m_evm15,
-		m_identifierAccess,
-		m_useNamedLabelsForFunctions,
-		localStackAdjustment,
-		m_context
-	)(_function.body);
+	try
+	{
+		CodeTransform(
+			m_assembly,
+			m_info,
+			_function.body,
+			m_allowStackOpt,
+			m_dialect,
+			m_evm15,
+			m_identifierAccess,
+			m_useNamedLabelsForFunctions,
+			localStackAdjustment,
+			m_context
+		)(_function.body);
+	}
+	catch (StackTooDeepError const& _error)
+	{
+		// This exception will be re-thrown after the end of the surrounding block.
+		// It enables us to see which functions compiled successfully and which did not.
+		// Even if we emit actual code, add an illegal instruction to make sure that tests
+		// will catch it.
+		StackTooDeepError error(_error);
+		if (error.functionName.empty())
+			error.functionName = _function.name;
+		stackError(error, height);
+	}
 
 	{
 		// The stack layout here is:
@@ -544,28 +570,34 @@ void CodeTransform::operator()(FunctionDefinition const& _function)
 			stackLayout.push_back(i); // Move return values down, but keep order.
 
 		if (stackLayout.size() > 17)
-			BOOST_THROW_EXCEPTION(StackTooDeepError() << errinfo_comment(
+		{
+			StackTooDeepError error(_function.name, YulString{}, stackLayout.size() - 17);
+			error << errinfo_comment(
 				"The function " +
 				_function.name.str() +
 				" has " +
 				to_string(stackLayout.size() - 17) +
 				" parameters or return variables too many to fit the stack size."
-			));
-		while (!stackLayout.empty() && stackLayout.back() != int(stackLayout.size() - 1))
-			if (stackLayout.back() < 0)
-			{
-				m_assembly.appendInstruction(solidity::Instruction::POP);
-				stackLayout.pop_back();
-			}
-			else
-			{
-				m_assembly.appendInstruction(swapInstruction(stackLayout.size() - stackLayout.back() - 1));
-				swap(stackLayout[stackLayout.back()], stackLayout.back());
-			}
-		for (int i = 0; size_t(i) < stackLayout.size(); ++i)
-			solAssert(i == stackLayout[i], "Error reshuffling stack.");
+			);
+			stackError(error, m_assembly.stackHeight() - _function.parameters.size());
+		}
+		else
+		{
+			while (!stackLayout.empty() && stackLayout.back() != int(stackLayout.size() - 1))
+				if (stackLayout.back() < 0)
+				{
+					m_assembly.appendInstruction(solidity::Instruction::POP);
+					stackLayout.pop_back();
+				}
+				else
+				{
+					m_assembly.appendInstruction(swapInstruction(stackLayout.size() - stackLayout.back() - 1));
+					swap(stackLayout[stackLayout.back()], stackLayout.back());
+				}
+			for (int i = 0; size_t(i) < stackLayout.size(); ++i)
+				solAssert(i == stackLayout[i], "Error reshuffling stack.");
+		}
 	}
-
 	if (m_evm15)
 		m_assembly.appendReturnsub(_function.returnVariables.size(), stackHeightBefore);
 	else
@@ -623,6 +655,9 @@ void CodeTransform::operator()(Block const& _block)
 
 	finalizeBlock(_block, blockStartStackHeight);
 	m_scope = originalScope;
+
+	if (!m_stackErrors.empty())
+		BOOST_THROW_EXCEPTION(m_stackErrors.front());
 }
 
 AbstractAssembly::LabelID CodeTransform::labelFromIdentifier(Identifier const& _identifier)
@@ -734,20 +769,24 @@ void CodeTransform::generateAssignment(Identifier const& _variableName)
 	}
 }
 
-int CodeTransform::variableHeightDiff(Scope::Variable const& _var, YulString _varName, bool _forSwap) const
+int CodeTransform::variableHeightDiff(Scope::Variable const& _var, YulString _varName, bool _forSwap)
 {
 	solAssert(m_context->variableStackHeights.count(&_var), "");
 	int heightDiff = m_assembly.stackHeight() - m_context->variableStackHeights[&_var];
 	solAssert(heightDiff > (_forSwap ? 1 : 0), "Negative stack difference for variable.");
 	int limit = _forSwap ? 17 : 16;
 	if (heightDiff > limit)
-		BOOST_THROW_EXCEPTION(StackTooDeepError() << errinfo_comment(
+	{
+		m_stackErrors.emplace_back(_varName, heightDiff - limit);
+		m_stackErrors.back() << errinfo_comment(
 			"Variable " +
 			_varName.str() +
 			" is " +
 			to_string(heightDiff - limit) +
 			" slot(s) too deep inside the stack."
-		));
+		);
+		BOOST_THROW_EXCEPTION(m_stackErrors.back());
+	}
 	return heightDiff;
 }
 

libyul/backends/evm/EVMCodeTransform.h

@@ -40,7 +40,16 @@ namespace yul
 struct AsmAnalysisInfo;
 class EVMAssembly;
 
-struct StackTooDeepError: virtual YulException {};
+struct StackTooDeepError: virtual YulException
+{
+	StackTooDeepError(YulString _variable, int _depth): variable(_variable), depth(_depth) {}
+	StackTooDeepError(YulString _functionName, YulString _variable, int _depth):
+		functionName(_functionName), variable(_variable), depth(_depth)
+	{}
+	YulString functionName;
+	YulString variable;
+	int depth;
+};
 
 struct CodeTransformContext
 {
@@ -115,6 +124,8 @@ public:
 	{
 	}
 
+	std::vector<StackTooDeepError> const& stackErrors() const { return m_stackErrors; }
+
 protected:
 	using Context = CodeTransformContext;
 
@@ -178,12 +189,16 @@ private:
 	/// Determines the stack height difference to the given variables. Throws
 	/// if it is not yet in scope or the height difference is too large. Returns
 	/// the (positive) stack height difference otherwise.
-	int variableHeightDiff(Scope::Variable const& _var, YulString _name, bool _forSwap) const;
+	int variableHeightDiff(Scope::Variable const& _var, YulString _name, bool _forSwap);
 
 	void expectDeposit(int _deposit, int _oldHeight) const;
 
 	void checkStackHeight(void const* _astElement) const;
 
+	/// Stores the stack error in the list of errors, appends an invalid opcode
+	/// and corrects the stack height to the target stack height.
+	void stackError(StackTooDeepError _error, int _targetStackSize);
+
 	AbstractAssembly& m_assembly;
 	AsmAnalysisInfo& m_info;
 	Scope* m_scope = nullptr;
@@ -204,6 +219,8 @@ private:
 	/// statement level in the scope where the variable was defined.
 	std::set<Scope::Variable const*> m_variablesScheduledForDeletion;
 	std::set<int> m_unusedStackSlots;
+
+	std::vector<StackTooDeepError> m_stackErrors;
 };
 
 }

libyul/backends/evm/EVMObjectCompiler.cpp

@@ -62,5 +62,7 @@ void EVMObjectCompiler::run(Object& _object, bool _optimize)
 	yulAssert(_object.code, "No code.");
 	// We do not catch and re-throw the stack too deep exception here because it is a YulException,
 	// which should be native to this part of the code.
-	CodeTransform{m_assembly, *_object.analysisInfo, *_object.code, m_dialect, _optimize, m_evm15}(*_object.code);
+	CodeTransform transform{m_assembly, *_object.analysisInfo, *_object.code, m_dialect, _optimize, m_evm15};
+	transform(*_object.code);
+	yulAssert(transform.stackErrors().empty(), "Stack errors present but not thrown.");
 }

libyul/backends/evm/NoOutputAssembly.cpp

@@ -0,0 +1,143 @@
+/*
+	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/>.
+*/
+/**
+ * Assembly interface that ignores everything. Can be used as a backend for a compilation dry-run.
+ */
+
+#include <libyul/backends/evm/NoOutputAssembly.h>
+
+#include <libevmasm/Instruction.h>
+
+#include <liblangutil/Exceptions.h>
+
+using namespace std;
+using namespace dev;
+using namespace langutil;
+using namespace yul;
+
+
+void NoOutputAssembly::appendInstruction(solidity::Instruction _instr)
+{
+	m_stackHeight += solidity::instructionInfo(_instr).ret - solidity::instructionInfo(_instr).args;
+}
+
+void NoOutputAssembly::appendConstant(u256 const&)
+{
+	appendInstruction(solidity::pushInstruction(1));
+}
+
+void NoOutputAssembly::appendLabel(LabelID)
+{
+	appendInstruction(solidity::Instruction::JUMPDEST);
+}
+
+void NoOutputAssembly::appendLabelReference(LabelID)
+{
+	solAssert(!m_evm15, "Cannot use plain label references in EMV1.5 mode.");
+	appendInstruction(solidity::pushInstruction(1));
+}
+
+NoOutputAssembly::LabelID NoOutputAssembly::newLabelId()
+{
+	return 1;
+}
+
+AbstractAssembly::LabelID NoOutputAssembly::namedLabel(string const&)
+{
+	return 1;
+}
+
+void NoOutputAssembly::appendLinkerSymbol(string const&)
+{
+	solAssert(false, "Linker symbols not yet implemented.");
+}
+
+void NoOutputAssembly::appendJump(int _stackDiffAfter)
+{
+	solAssert(!m_evm15, "Plain JUMP used for EVM 1.5");
+	appendInstruction(solidity::Instruction::JUMP);
+	m_stackHeight += _stackDiffAfter;
+}
+
+void NoOutputAssembly::appendJumpTo(LabelID _labelId, int _stackDiffAfter)
+{
+	if (m_evm15)
+		m_stackHeight += _stackDiffAfter;
+	else
+	{
+		appendLabelReference(_labelId);
+		appendJump(_stackDiffAfter);
+	}
+}
+
+void NoOutputAssembly::appendJumpToIf(LabelID _labelId)
+{
+	if (m_evm15)
+		m_stackHeight--;
+	else
+	{
+		appendLabelReference(_labelId);
+		appendInstruction(solidity::Instruction::JUMPI);
+	}
+}
+
+void NoOutputAssembly::appendBeginsub(LabelID, int _arguments)
+{
+	solAssert(m_evm15, "BEGINSUB used for EVM 1.0");
+	solAssert(_arguments >= 0, "");
+	m_stackHeight += _arguments;
+}
+
+void NoOutputAssembly::appendJumpsub(LabelID, int _arguments, int _returns)
+{
+	solAssert(m_evm15, "JUMPSUB used for EVM 1.0");
+	solAssert(_arguments >= 0 && _returns >= 0, "");
+	m_stackHeight += _returns - _arguments;
+}
+
+void NoOutputAssembly::appendReturnsub(int _returns, int _stackDiffAfter)
+{
+	solAssert(m_evm15, "RETURNSUB used for EVM 1.0");
+	solAssert(_returns >= 0, "");
+	m_stackHeight += _stackDiffAfter - _returns;
+}
+
+void NoOutputAssembly::appendAssemblySize()
+{
+	appendInstruction(solidity::Instruction::PUSH1);
+}
+
+pair<shared_ptr<AbstractAssembly>, AbstractAssembly::SubID> NoOutputAssembly::createSubAssembly()
+{
+	solAssert(false, "Sub assemblies not implemented.");
+	return {};
+}
+
+void NoOutputAssembly::appendDataOffset(AbstractAssembly::SubID)
+{
+	appendInstruction(solidity::Instruction::PUSH1);
+}
+
+void NoOutputAssembly::appendDataSize(AbstractAssembly::SubID)
+{
+	appendInstruction(solidity::Instruction::PUSH1);
+}
+
+AbstractAssembly::SubID NoOutputAssembly::appendData(bytes const&)
+{
+	return 1;
+}

libyul/backends/evm/NoOutputAssembly.h

@@ -0,0 +1,75 @@
+/*
+	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/>.
+*/
+/**
+ * Assembly interface that ignores everything. Can be used as a backend for a compilation dry-run.
+ */
+
+#pragma once
+
+#include <libyul/backends/evm/AbstractAssembly.h>
+
+#include <libevmasm/LinkerObject.h>
+
+#include <map>
+
+namespace langutil
+{
+struct SourceLocation;
+}
+
+namespace yul
+{
+
+/**
+ * Assembly class that just ignores everything and only performs stack counting.
+ * The purpose is to use this assembly for compilation dry-runs.
+ */
+class NoOutputAssembly: public AbstractAssembly
+{
+public:
+	explicit NoOutputAssembly(bool _evm15 = false): m_evm15(_evm15) { }
+	virtual ~NoOutputAssembly() = default;
+
+	void setSourceLocation(langutil::SourceLocation const&) override {}
+	int stackHeight() const override { return m_stackHeight; }
+	void appendInstruction(dev::solidity::Instruction _instruction) override;
+	void appendConstant(dev::u256 const& _constant) override;
+	void appendLabel(LabelID _labelId) override;
+	void appendLabelReference(LabelID _labelId) override;
+	LabelID newLabelId() override;
+	LabelID namedLabel(std::string const& _name) override;
+	void appendLinkerSymbol(std::string const& _name) override;
+
+	void appendJump(int _stackDiffAfter) override;
+	void appendJumpTo(LabelID _labelId, int _stackDiffAfter) override;
+	void appendJumpToIf(LabelID _labelId) override;
+	void appendBeginsub(LabelID _labelId, int _arguments) override;
+	void appendJumpsub(LabelID _labelId, int _arguments, int _returns) override;
+	void appendReturnsub(int _returns, int _stackDiffAfter) override;
+
+	void appendAssemblySize() override;
+	std::pair<std::shared_ptr<AbstractAssembly>, SubID> createSubAssembly() override;
+	void appendDataOffset(SubID _sub) override;
+	void appendDataSize(SubID _sub) override;
+	SubID appendData(dev::bytes const& _data) override;
+
+private:
+	bool m_evm15 = false; ///< if true, switch to evm1.5 mode
+	int m_stackHeight = 0;
+};
+
+}

test/libyul/CompilabilityChecker.cpp

@@ -0,0 +1,225 @@
+/*
+    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/>.
+*/
+/**
+ * Unit tests for the compilability checker.
+ */
+
+#include <test/Options.h>
+
+#include <test/libyul/Common.h>
+#include <libyul/backends/evm/EVMDialect.h>
+
+#include <libyul/CompilabilityChecker.h>
+
+
+using namespace std;
+
+namespace yul
+{
+namespace test
+{
+
+namespace
+{
+string check(string const& _input)
+{
+	shared_ptr<Block> ast = yul::test::parse(_input, false).first;
+	BOOST_REQUIRE(ast);
+	map<YulString, int> functions = CompilabilityChecker::run(EVMDialect::strictAssemblyForEVM(), *ast);
+	string out;
+	for (auto const& function: functions)
+		out += function.first.str() + ": " + to_string(function.second) + " ";
+	return out;
+}
+}
+
+BOOST_AUTO_TEST_SUITE(CompilabilityChecker)
+
+BOOST_AUTO_TEST_CASE(smoke_test)
+{
+	string out = check("{}");
+	BOOST_CHECK_EQUAL(out, "");
+}
+
+BOOST_AUTO_TEST_CASE(simple_function)
+{
+	string out = check("{ function f(a, b) -> x, y { x := a y := b } }");
+	BOOST_CHECK_EQUAL(out, "");
+}
+
+BOOST_AUTO_TEST_CASE(many_variables_few_uses)
+{
+	string out = check(R"({
+		function f(a, b) -> x, y {
+			let r1 := 0
+			let r2 := 0
+			let r3 := 0
+			let r4 := 0
+			let r5 := 0
+			let r6 := 0
+			let r7 := 0
+			let r8 := 0
+			let r9 := 0
+			let r10 := 0
+			let r11 := 0
+			let r12 := 0
+			let r13 := 0
+			let r14 := 0
+			let r15 := 0
+			let r16 := 0
+			let r17 := 0
+			let r18 := 0
+			x := add(add(add(add(add(add(add(add(add(x, r9), r8), r7), r6), r5), r4), r3), r2), r1)
+		}
+	})");
+	BOOST_CHECK_EQUAL(out, "f: 4 ");
+}
+
+BOOST_AUTO_TEST_CASE(many_variables_many_uses)
+{
+	string out = check(R"({
+		function f(a, b) -> x, y {
+			let r1 := 0
+			let r2 := 0
+			let r3 := 0
+			let r4 := 0
+			let r5 := 0
+			let r6 := 0
+			let r7 := 0
+			let r8 := 0
+			let r9 := 0
+			let r10 := 0
+			let r11 := 0
+			let r12 := 0
+			let r13 := 0
+			let r14 := 0
+			let r15 := 0
+			let r16 := 0
+			let r17 := 0
+			let r18 := 0
+			x := add(add(add(add(add(add(add(add(add(add(add(add(x, r12), r11), r10), r9), r8), r7), r6), r5), r4), r3), r2), r1)
+		}
+	})");
+	BOOST_CHECK_EQUAL(out, "f: 10 ");
+}
+
+BOOST_AUTO_TEST_CASE(many_return_variables)
+{
+	string out = check(R"({
+		function f(a, b) -> r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15, r16, r17, r18, r19 {
+		}
+	})");
+	BOOST_CHECK_EQUAL(out, "f: 5 ");
+}
+
+BOOST_AUTO_TEST_CASE(multiple_functions)
+{
+	string out = check(R"({
+		function f(a, b) -> r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15, r16, r17, r18, r19 {
+		}
+		function g(r1, r2, r3, r4, r5, r6, r7, r8, r9, r10, r11, r12, r13, r14, r15, r16, r17, r18, r19) -> x, y {
+		}
+		function h(x) {
+			let r1 := 0
+			let r2 := 0
+			let r3 := 0
+			let r4 := 0
+			let r5 := 0
+			let r6 := 0
+			let r7 := 0
+			let r8 := 0
+			let r9 := 0
+			let r10 := 0
+			let r11 := 0
+			let r12 := 0
+			let r13 := 0
+			let r14 := 0
+			let r15 := 0
+			let r16 := 0
+			let r17 := 0
+			let r18 := 0
+			x := add(add(add(add(add(add(add(add(add(add(add(add(x, r12), r11), r10), r9), r8), r7), r6), r5), r4), r3), r2), r1)
+		}
+	})");
+	BOOST_CHECK_EQUAL(out, "h: 9 g: 5 f: 5 ");
+}
+
+BOOST_AUTO_TEST_CASE(nested)
+{
+	string out = check(R"({
+		function h(x) {
+			let r1 := 0
+			let r2 := 0
+			let r3 := 0
+			let r4 := 0
+			let r5 := 0
+			let r6 := 0
+			let r7 := 0
+			let r8 := 0
+			let r9 := 0
+			let r10 := 0
+			let r11 := 0
+			let r12 := 0
+			let r13 := 0
+			let r14 := 0
+			let r15 := 0
+			let r16 := 0
+			let r17 := 0
+			let r18 := 0
+			function f(a, b) -> t1, t2, t3, t4, t5, t6, t7, t8, t9, t10, t11, t12, t13, t14, t15, t16, t17, t18, t19 {
+				function g(s1, s2, s3, s4, s5, s6, s7, s8, s9, s10, s11, s12, s13, s14, s15, s16, s17, s18, s19) -> w, v {
+				}
+			}
+			x := add(add(add(add(add(add(add(add(add(add(add(add(x, r12), r11), r10), r9), r8), r7), r6), r5), r4), r3), r2), r1)
+		}
+	})");
+	BOOST_CHECK_EQUAL(out, "h: 9 ");
+}
+
+BOOST_AUTO_TEST_CASE(also_in_outer_block)
+{
+	string out = check(R"({
+			let x := 0
+			let r1 := 0
+			let r2 := 0
+			let r3 := 0
+			let r4 := 0
+			let r5 := 0
+			let r6 := 0
+			let r7 := 0
+			let r8 := 0
+			let r9 := 0
+			let r10 := 0
+			let r11 := 0
+			let r12 := 0
+			let r13 := 0
+			let r14 := 0
+			let r15 := 0
+			let r16 := 0
+			let r17 := 0
+			let r18 := 0
+			x := add(add(add(add(add(add(add(add(add(add(add(add(x, r12), r11), r10), r9), r8), r7), r6), r5), r4), r3), r2), r1)
+			function g(s1, s2, s3, s4, s5, s6, s7, s8, s9, s10, s11, s12, s13, s14, s15, s16, s17, s18, s19) -> w, v {
+			}
+	})");
+	BOOST_CHECK_EQUAL(out, ": 9 ");
+}
+
+BOOST_AUTO_TEST_SUITE_END()
+
+}
+}