3 files changed, 55 insertions, 38 deletions

diff --git a/libsolidity/codegen/ContractCompiler.cpp b/libsolidity/codegen/ContractCompiler.cpp
index bcfd33f2..715852be 100644
--- a/libsolidity/codegen/ContractCompiler.cpp
+++ b/libsolidity/codegen/ContractCompiler.cpp
@@ -431,16 +431,16 @@ bool ContractCompiler::visit(FunctionDefinition const& _function)
 		if (auto c = m_context.nextConstructor(dynamic_cast<ContractDefinition const&>(*_function.scope())))
 			appendBaseConstructor(*c);
 
-	m_returnTag = m_context.newTag();
+	solAssert(m_returnTags.empty(), "");
 	m_breakTags.clear();
 	m_continueTags.clear();
 	m_stackCleanupForReturn = 0;
 	m_currentFunction = &_function;
-	m_modifierDepth = 0;
+	m_modifierDepth = -1;
 
 	appendModifierOrFunctionCode();
 
-	m_context << m_returnTag;
+	solAssert(m_returnTags.empty(), "");
 
 	// Now we need to re-shuffle the stack. For this we keep a record of the stack layout
 	// that shows the target positions of the elements, where "-1" denotes that this element needs
@@ -695,7 +695,7 @@ bool ContractCompiler::visit(Return const& _return)
 	}
 	for (unsigned i = 0; i < m_stackCleanupForReturn; ++i)
 		m_context << Instruction::POP;
-	m_context.appendJumpTo(m_returnTag);
+	m_context.appendJumpTo(m_returnTags.back());
 	m_context.adjustStackOffset(m_stackCleanupForReturn);
 	return false;
 }
@@ -755,9 +755,7 @@ bool ContractCompiler::visit(PlaceholderStatement const& _placeholderStatement)
 {
 	StackHeightChecker checker(m_context);
 	CompilerContext::LocationSetter locationSetter(m_context, _placeholderStatement);
-	++m_modifierDepth;
 	appendModifierOrFunctionCode();
-	--m_modifierDepth;
 	checker.check();
 	return true;
 }
@@ -775,10 +773,15 @@ void ContractCompiler::appendMissingFunctions()
 void ContractCompiler::appendModifierOrFunctionCode()
 {
 	solAssert(m_currentFunction, "");
+	unsigned stackSurplus = 0;
+	Block const* codeBlock = nullptr;
+
+	m_modifierDepth++;
+
 	if (m_modifierDepth >= m_currentFunction->modifiers().size())
 	{
 		solAssert(m_currentFunction->isImplemented(), "");
-		m_currentFunction->body().accept(*this);
+		codeBlock = &m_currentFunction->body();
 	}
 	else
 	{
@@ -786,37 +789,45 @@ void ContractCompiler::appendModifierOrFunctionCode()
 
 		// constructor call should be excluded
 		if (dynamic_cast<ContractDefinition const*>(modifierInvocation->name()->annotation().referencedDeclaration))
-		{
-			++m_modifierDepth;
 			appendModifierOrFunctionCode();
-			--m_modifierDepth;
-			return;
-		}
-
-		ModifierDefinition const& modifier = m_context.functionModifier(modifierInvocation->name()->name());
-		CompilerContext::LocationSetter locationSetter(m_context, modifier);
-		solAssert(modifier.parameters().size() == modifierInvocation->arguments().size(), "");
-		for (unsigned i = 0; i < modifier.parameters().size(); ++i)
+		else
 		{
-			m_context.addVariable(*modifier.parameters()[i]);
-			compileExpression(
-				*modifierInvocation->arguments()[i],
-				modifier.parameters()[i]->annotation().type
-			);
+			ModifierDefinition const& modifier = m_context.functionModifier(modifierInvocation->name()->name());
+			CompilerContext::LocationSetter locationSetter(m_context, modifier);
+			solAssert(modifier.parameters().size() == modifierInvocation->arguments().size(), "");
+			for (unsigned i = 0; i < modifier.parameters().size(); ++i)
+			{
+				m_context.addVariable(*modifier.parameters()[i]);
+				compileExpression(
+					*modifierInvocation->arguments()[i],
+					modifier.parameters()[i]->annotation().type
+				);
+			}
+			for (VariableDeclaration const* localVariable: modifier.localVariables())
+				appendStackVariableInitialisation(*localVariable);
+
+			stackSurplus =
+				CompilerUtils::sizeOnStack(modifier.parameters()) +
+				CompilerUtils::sizeOnStack(modifier.localVariables());
+			codeBlock = &modifier.body();
+
+			codeBlock = &modifier.body();
 		}
-		for (VariableDeclaration const* localVariable: modifier.localVariables())
-			appendStackVariableInitialisation(*localVariable);
+	}
+
+	if (codeBlock)
+	{
+		m_returnTags.push_back(m_context.newTag());
 
-		unsigned const c_stackSurplus = CompilerUtils::sizeOnStack(modifier.parameters()) +
-										CompilerUtils::sizeOnStack(modifier.localVariables());
-		m_stackCleanupForReturn += c_stackSurplus;
+		codeBlock->accept(*this);
 
-		modifier.body().accept(*this);
+		solAssert(!m_returnTags.empty(), "");
+		m_context << m_returnTags.back();
+		m_returnTags.pop_back();
 
-		for (unsigned i = 0; i < c_stackSurplus; ++i)
-			m_context << Instruction::POP;
-		m_stackCleanupForReturn -= c_stackSurplus;
+		CompilerUtils(m_context).popStackSlots(stackSurplus);
 	}
+	m_modifierDepth--;
 }
 
 void ContractCompiler::appendStackVariableInitialisation(VariableDeclaration const& _variable)
diff --git a/libsolidity/codegen/ContractCompiler.h b/libsolidity/codegen/ContractCompiler.h
index d1517e88..0799a543 100644
--- a/libsolidity/codegen/ContractCompiler.h
+++ b/libsolidity/codegen/ContractCompiler.h
@@ -40,11 +40,9 @@ class ContractCompiler: private ASTConstVisitor
 public:
 	explicit ContractCompiler(CompilerContext& _context, bool _optimise):
 		m_optimise(_optimise),
-		m_context(_context),
-		m_returnTag(eth::Tag, u256(-1))
+		m_context(_context)
 	{
 		m_context = CompilerContext();
-		m_returnTag = m_context.newTag();
 	}
 
 	void compileContract(
@@ -122,7 +120,8 @@ private:
 	CompilerContext& m_context;
 	std::vector<eth::AssemblyItem> m_breakTags; ///< tag to jump to for a "break" statement
 	std::vector<eth::AssemblyItem> m_continueTags; ///< tag to jump to for a "continue" statement
-	eth::AssemblyItem m_returnTag; ///< tag to jump to for a "return" statement
+	/// Tag to jump to for a "return" statement, needs to be stacked because of modifiers.
+	std::vector<eth::AssemblyItem> m_returnTags;
 	unsigned m_modifierDepth = 0;
 	FunctionDefinition const* m_currentFunction = nullptr;
 	unsigned m_stackCleanupForReturn = 0; ///< this number of stack elements need to be removed before jump to m_returnTag
diff --git a/libsolidity/codegen/ExpressionCompiler.cpp b/libsolidity/codegen/ExpressionCompiler.cpp
index e8350931..4a81e27d 100644
--- a/libsolidity/codegen/ExpressionCompiler.cpp
+++ b/libsolidity/codegen/ExpressionCompiler.cpp
@@ -1324,11 +1324,18 @@ void ExpressionCompiler::appendArithmeticOperatorCode(Token::Value _operator, Ty
 		m_context << Instruction::MUL;
 		break;
 	case Token::Div:
-		m_context  << (c_isSigned ? Instruction::SDIV : Instruction::DIV);
-		break;
 	case Token::Mod:
-		m_context << (c_isSigned ? Instruction::SMOD : Instruction::MOD);
+	{
+		// Test for division by zero
+		m_context << Instruction::DUP2 << Instruction::ISZERO;
+		m_context.appendConditionalJumpTo(m_context.errorTag());
+
+		if (_operator == Token::Div)
+			m_context << (c_isSigned ? Instruction::SDIV : Instruction::DIV);
+		else
+			m_context << (c_isSigned ? Instruction::SMOD : Instruction::MOD);
 		break;
+	}
 	case Token::Exp:
 		m_context << Instruction::EXP;
 		break;