Support empty strings.

libsolidity/AST.cpp

@@ -339,7 +339,7 @@ void Literal::checkTypeRequirements()
 {
 	m_type = Type::forLiteral(*this);
 	if (!m_type)
-		BOOST_THROW_EXCEPTION(createTypeError("Literal value too large or too small."));
+		BOOST_THROW_EXCEPTION(createTypeError("Literal value too large."));
 }
 
 }

libsolidity/Compiler.cpp

@@ -135,7 +135,7 @@ unsigned Compiler::appendCalldataUnpacker(FunctionDefinition const& _function, b
 	for (ASTPointer<VariableDeclaration> const& var: _function.getParameters())
 	{
 		unsigned const numBytes = var->getType()->getCalldataEncodedSize();
-		if (numBytes == 0 || numBytes > 32)
+		if (numBytes > 32)
 			BOOST_THROW_EXCEPTION(CompilerError()
 								  << errinfo_sourceLocation(var->getLocation())
 								  << errinfo_comment("Type " + var->getType()->toString() + " not yet supported."));
@@ -156,7 +156,7 @@ void Compiler::appendReturnValuePacker(FunctionDefinition const& _function)
 	{
 		Type const& paramType = *parameters[i]->getType();
 		unsigned numBytes = paramType.getCalldataEncodedSize();
-		if (numBytes == 0 || numBytes > 32)
+		if (numBytes > 32)
 			BOOST_THROW_EXCEPTION(CompilerError()
 								  << errinfo_sourceLocation(parameters[i]->getLocation())
 								  << errinfo_comment("Type " + paramType.toString() + " not yet supported."));

libsolidity/CompilerUtils.cpp

@@ -33,9 +33,14 @@ namespace solidity
 
 void CompilerUtils::loadFromMemory(unsigned _offset, unsigned _bytes, bool _leftAligned, bool _fromCalldata)
 {
+	if (_bytes == 0)
+	{
+		m_context << u256(0);
+		return;
+	}
 	eth::Instruction load = _fromCalldata ? eth::Instruction::CALLDATALOAD : eth::Instruction::MLOAD;
-	if (asserts(0 < _bytes && _bytes <= 32))
-		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Memory load of 0 or more than 32 bytes requested."));
+	if (asserts(_bytes <= 32))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Memory load of more than 32 bytes requested."));
 	if (_bytes == 32)
 		m_context << u256(_offset) << load;
 	else
@@ -53,8 +58,13 @@ void CompilerUtils::loadFromMemory(unsigned _offset, unsigned _bytes, bool _left
 
 void CompilerUtils::storeInMemory(unsigned _offset, unsigned _bytes, bool _leftAligned)
 {
-	if (asserts(0 < _bytes && _bytes <= 32))
-		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Memory store of 0 or more than 32 bytes requested."));
+	if (_bytes == 0)
+	{
+		m_context << eth::Instruction::POP;
+		return;
+	}
+	if (asserts(_bytes <= 32))
+		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Memory store of more than 32 bytes requested."));
 	if (_bytes != 32 && !_leftAligned)
 		// shift the value accordingly before storing
 		m_context << (u256(1) << ((32 - _bytes) * 8)) << eth::Instruction::MUL;

libsolidity/Token.h

@@ -269,6 +269,7 @@ namespace solidity
 	K(ADDRESS, "address", 0)                                           \
 	K(BOOL, "bool", 0)                                                 \
 	K(STRING_TYPE, "string", 0)                                        \
+	K(STRING0, "string0", 0)                                           \
 	K(STRING1, "string1", 0)                                           \
 	K(STRING2, "string2", 0)                                           \
 	K(STRING3, "string3", 0)                                           \

libsolidity/Types.cpp

@@ -53,8 +53,8 @@ shared_ptr<Type const> Type::fromElementaryTypeName(Token::Value _typeToken)
 		return make_shared<IntegerType const>(0, IntegerType::Modifier::ADDRESS);
 	else if (_typeToken == Token::BOOL)
 		return make_shared<BoolType const>();
-	else if (Token::STRING1 <= _typeToken && _typeToken <= Token::STRING32)
-		return make_shared<StaticStringType const>(int(_typeToken) - int(Token::STRING1) + 1);
+	else if (Token::STRING0 <= _typeToken && _typeToken <= Token::STRING32)
+		return make_shared<StaticStringType const>(int(_typeToken) - int(Token::STRING0));
 	else
 		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Unable to convert elementary typename " +
 																		 std::string(Token::toString(_typeToken)) + " to type."));
@@ -199,14 +199,14 @@ const MemberList IntegerType::AddressMemberList =
 
 shared_ptr<StaticStringType> StaticStringType::smallestTypeForLiteral(string const& _literal)
 {
-	if (0 < _literal.length() && _literal.length() <= 32)
+	if (_literal.length() <= 32)
 		return make_shared<StaticStringType>(_literal.length());
 	return shared_ptr<StaticStringType>();
 }
 
 StaticStringType::StaticStringType(int _bytes): m_bytes(_bytes)
 {
-	if (asserts(m_bytes > 0 && m_bytes <= 32))
+	if (asserts(m_bytes >= 0 && m_bytes <= 32))
 		BOOST_THROW_EXCEPTION(InternalCompilerError() << errinfo_comment("Invalid byte number for static string type: " +
 																		 dev::toString(m_bytes)));
 }

test/solidityEndToEndTest.cpp

@@ -510,6 +510,20 @@ BOOST_AUTO_TEST_CASE(strings)
 	BOOST_CHECK(callContractFunction(1, bytes({0x00, 0x02, 0x01})) == expectation);
 }
 
+BOOST_AUTO_TEST_CASE(empty_string_on_stack)
+{
+	char const* sourceCode = "contract test {\n"
+							 "  function run(string0 empty, uint8 inp) returns(uint16 a, string0 b, string4 c) {\n"
+							 "    var x = \"abc\";\n"
+							 "    var y = \"\";\n"
+							 "    var z = inp;\n"
+							 "    a = z; b = y; c = x;"
+							 "  }\n"
+							 "}\n";
+	compileAndRun(sourceCode);
+	BOOST_CHECK(callContractFunction(0, bytes({0x02})) == bytes({0x00, 0x02, 'a', 'b', 'c', 0x00}));
+}
+
 BOOST_AUTO_TEST_CASE(state_smoke_test)
 {
 	char const* sourceCode = "contract test {\n"

test/solidityNameAndTypeResolution.cpp

@@ -226,14 +226,6 @@ BOOST_AUTO_TEST_CASE(type_inference_explicit_conversion)
 	BOOST_CHECK_NO_THROW(parseTextAndResolveNames(text));
 }
 
-BOOST_AUTO_TEST_CASE(empty_string_literal)
-{
-	char const* text = "contract test {\n"
-					   "  function f() { var x = \"\"; }"
-					   "}\n";
-	BOOST_CHECK_THROW(parseTextAndResolveNames(text), TypeError);
-}
-
 BOOST_AUTO_TEST_CASE(large_string_literal)
 {
 	char const* text = "contract test {\n"