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Merge pull request #1729 from ethereum/constantvariables

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Only allow pure expressions for constant state variables.
This commit is contained in:
Yoichi Hirai 2017-03-15 10:03:35 +01:00 committed by GitHub
commit d134fda0c0
8 changed files with 241 additions and 35 deletions
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1
Changelog.md
View File

@ -20,6 +20,7 @@ Bugfixes:
* Type system: Detect cyclic dependencies between constants.
* Type system: Disallow arrays with negative length.
* Type system: Fix a crash related to invalid binary operators.
* Type system: Warn if constant state variables are not compile-time constants.
* Type system: Disallow ``var`` declaration with empty tuple type.
* Type system: Correctly convert function argument types to pointers for member functions.
* Type system: Move privateness of constructor into AST itself.

26
docs/contracts.rst
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@ -428,8 +428,25 @@ change by overriding).
Constant State Variables
************************
State variables can be declared as constant (this is not yet implemented
for array and struct types and not possible for mapping types).
State variables can be declared as ``constant``. In this case, they have to be
assigned from an expression which is a constant at compile time. Any expression
that accesses storage, blockchain data (e.g. ``now``, ``this.balance`` or
``block.number``) or
execution data (``msg.gas``) or make calls to external contracts are disallowed. Expressions
that might have a side-effect on memory allocation are allowed, but those that
might have a side-effect on other memory objects are not. The built-in functions
``keccak256``, ``sha256``, ``ripemd160``, ``ecrecover``, ``addmod`` and ``mulmod``
are allowed (ever though they do call external contracts).
The reason behind allowing side-effects on the memory allocator is that it
should be possible to construct complex objects like e.g. lookup-tables.
This feature is not yet fully usable.
The compiler does not reserve a storage slot for these variables and every occurrence is
replaced by the respective constant expression (which might be computed to a single value by the optimizer).
Not all types for constants are implemented at this time. The only supported types are
value types and strings.
::
@ -438,12 +455,9 @@ for array and struct types and not possible for mapping types).
contract C {
uint constant x = 32**22 + 8;
string constant text = "abc";
bytes32 constant myHash = keccak256("abc");
}
This has the effect that the compiler does not reserve a storage slot
for these variables and every occurrence is replaced by their constant value.
The value expression can only contain integer arithmetics.
******************
Constant Functions

88
libsolidity/analysis/TypeChecker.cpp
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@ -467,27 +467,29 @@ bool TypeChecker::visit(VariableDeclaration const& _variable)
// TypeChecker at the VariableDeclarationStatement level.
TypePointer varType = _variable.annotation().type;
solAssert(!!varType, "Failed to infer variable type.");
if (_variable.isConstant())
{
if (!dynamic_cast<ContractDefinition const*>(_variable.scope()))
typeError(_variable.location(), "Illegal use of \"constant\" specifier.");
if (!_variable.value())
typeError(_variable.location(), "Uninitialized \"constant\" variable.");
if (!varType->isValueType())
{
bool constImplemented = false;
if (auto arrayType = dynamic_cast<ArrayType const*>(varType.get()))
constImplemented = arrayType->isByteArray();
if (!constImplemented)
typeError(
_variable.location(),
"Illegal use of \"constant\" specifier. \"constant\" "
"is not yet implemented for this type."
);
}
}
if (_variable.value())
expectType(*_variable.value(), *varType);
if (_variable.isConstant())
{
if (!_variable.isStateVariable())
typeError(_variable.location(), "Illegal use of \"constant\" specifier.");
if (!_variable.type()->isValueType())
{
bool allowed = false;
if (auto arrayType = dynamic_cast<ArrayType const*>(_variable.type().get()))
allowed = arrayType->isString();
if (!allowed)
typeError(_variable.location(), "Constants of non-value type not yet implemented.");
}
if (!_variable.value())
typeError(_variable.location(), "Uninitialized \"constant\" variable.");
else if (!_variable.value()->annotation().isPure)
warning(
_variable.value()->location(),
"Initial value for constant variable has to be compile-time constant. "
"This will fail to compile with the next breaking version change."
);
}
if (!_variable.isStateVariable())
{
if (varType->dataStoredIn(DataLocation::Memory) || varType->dataStoredIn(DataLocation::CallData))
@ -928,6 +930,10 @@ bool TypeChecker::visit(Conditional const& _conditional)
}
_conditional.annotation().type = commonType;
_conditional.annotation().isPure =
_conditional.condition().annotation().isPure &&
_conditional.trueExpression().annotation().isPure &&
_conditional.falseExpression().annotation().isPure;
if (_conditional.annotation().lValueRequested)
typeError(
@ -1009,6 +1015,7 @@ bool TypeChecker::visit(TupleExpression const& _tuple)
}
else
{
bool isPure = true;
TypePointer inlineArrayType;
for (size_t i = 0; i < components.size(); ++i)
{
@ -1031,10 +1038,13 @@ bool TypeChecker::visit(TupleExpression const& _tuple)
else if (inlineArrayType)
inlineArrayType = Type::commonType(inlineArrayType, types[i]);
}
if (!components[i]->annotation().isPure)
isPure = false;
}
else
types.push_back(TypePointer());
}
_tuple.annotation().isPure = isPure;
if (_tuple.isInlineArray())
{
if (!inlineArrayType)
@ -1061,7 +1071,8 @@ bool TypeChecker::visit(UnaryOperation const& _operation)
{
// Inc, Dec, Add, Sub, Not, BitNot, Delete
Token::Value op = _operation.getOperator();
if (op == Token::Value::Inc || op == Token::Value::Dec || op == Token::Value::Delete)
bool const modifying = (op == Token::Value::Inc || op == Token::Value::Dec || op == Token::Value::Delete);
if (modifying)
requireLValue(_operation.subExpression());
else
_operation.subExpression().accept(*this);
@ -1079,6 +1090,7 @@ bool TypeChecker::visit(UnaryOperation const& _operation)
t = subExprType;
}
_operation.annotation().type = t;
_operation.annotation().isPure = !modifying && _operation.subExpression().annotation().isPure;
return false;
}
@ -1105,6 +1117,10 @@ void TypeChecker::endVisit(BinaryOperation const& _operation)
Token::isCompareOp(_operation.getOperator()) ?
make_shared<BoolType>() :
commonType;
_operation.annotation().isPure =
_operation.leftExpression().annotation().isPure &&
_operation.rightExpression().annotation().isPure;
if (_operation.getOperator() == Token::Exp)
{
if (
@ -1133,6 +1149,8 @@ bool TypeChecker::visit(FunctionCall const& _functionCall)
vector<ASTPointer<Expression const>> arguments = _functionCall.arguments();
vector<ASTPointer<ASTString>> const& argumentNames = _functionCall.names();
bool isPure = true;
// We need to check arguments' type first as they will be needed for overload resolution.
shared_ptr<TypePointers> argumentTypes;
if (isPositionalCall)
@ -1140,6 +1158,8 @@ bool TypeChecker::visit(FunctionCall const& _functionCall)
for (ASTPointer<Expression const> const& argument: arguments)
{
argument->accept(*this);
if (!argument->annotation().isPure)
isPure = false;
// only store them for positional calls
if (isPositionalCall)
argumentTypes->push_back(type(*argument));
@ -1177,6 +1197,7 @@ bool TypeChecker::visit(FunctionCall const& _functionCall)
typeError(_functionCall.location(), "Explicit type conversion not allowed.");
}
_functionCall.annotation().type = resultType;
_functionCall.annotation().isPure = isPure;
return false;
}
@ -1193,9 +1214,16 @@ bool TypeChecker::visit(FunctionCall const& _functionCall)
auto const& structType = dynamic_cast<StructType const&>(*t.actualType());
functionType = structType.constructorType();
membersRemovedForStructConstructor = structType.membersMissingInMemory();
_functionCall.annotation().isPure = isPure;
}
else
{
functionType = dynamic_pointer_cast<FunctionType const>(expressionType);
_functionCall.annotation().isPure =
isPure &&
_functionCall.expression().annotation().isPure &&
functionType->isPure();
}
if (!functionType)
{
@ -1360,6 +1388,7 @@ void TypeChecker::endVisit(NewExpression const& _newExpression)
strings(),
FunctionType::Location::ObjectCreation
);
_newExpression.annotation().isPure = true;
}
else
fatalTypeError(_newExpression.location(), "Contract or array type expected.");
@ -1445,6 +1474,12 @@ bool TypeChecker::visit(MemberAccess const& _memberAccess)
annotation.isLValue = annotation.referencedDeclaration->isLValue();
}
// TODO some members might be pure, but for example `address(0x123).balance` is not pure
// although every subexpression is, so leaving this limited for now.
if (auto tt = dynamic_cast<TypeType const*>(exprType.get()))
if (tt->actualType()->category() == Type::Category::Enum)
annotation.isPure = true;
return false;
}
@ -1454,6 +1489,7 @@ bool TypeChecker::visit(IndexAccess const& _access)
TypePointer baseType = type(_access.baseExpression());
TypePointer resultType;
bool isLValue = false;
bool isPure = _access.baseExpression().annotation().isPure;
Expression const* index = _access.indexExpression();
switch (baseType->category())
{
@ -1535,6 +1571,9 @@ bool TypeChecker::visit(IndexAccess const& _access)
}
_access.annotation().type = move(resultType);
_access.annotation().isLValue = isLValue;
if (index && !index->annotation().isPure)
isPure = false;
_access.annotation().isPure = isPure;
return false;
}
@ -1589,18 +1628,22 @@ bool TypeChecker::visit(Identifier const& _identifier)
!!annotation.referencedDeclaration,
"Referenced declaration is null after overload resolution."
);
auto variableDeclaration = dynamic_cast<VariableDeclaration const*>(annotation.referencedDeclaration);
annotation.isConstant = variableDeclaration != nullptr && variableDeclaration->isConstant();
annotation.isLValue = annotation.referencedDeclaration->isLValue();
annotation.type = annotation.referencedDeclaration->type();
if (!annotation.type)
fatalTypeError(_identifier.location(), "Declaration referenced before type could be determined.");
if (auto variableDeclaration = dynamic_cast<VariableDeclaration const*>(annotation.referencedDeclaration))
annotation.isPure = annotation.isConstant = variableDeclaration->isConstant();
else if (dynamic_cast<MagicVariableDeclaration const*>(annotation.referencedDeclaration))
if (auto functionType = dynamic_cast<FunctionType const*>(annotation.type.get()))
annotation.isPure = functionType->isPure();
return false;
}
void TypeChecker::endVisit(ElementaryTypeNameExpression const& _expr)
{
_expr.annotation().type = make_shared<TypeType>(Type::fromElementaryTypeName(_expr.typeName()));
_expr.annotation().isPure = true;
}
void TypeChecker::endVisit(Literal const& _literal)
@ -1620,6 +1663,7 @@ void TypeChecker::endVisit(Literal const& _literal)
);
}
_literal.annotation().type = Type::forLiteral(_literal);
_literal.annotation().isPure = true;
if (!_literal.annotation().type)
fatalTypeError(_literal.location(), "Invalid literal value.");
}

2
libsolidity/ast/ASTAnnotations.h
View File

@ -156,6 +156,8 @@ struct ExpressionAnnotation: ASTAnnotation
TypePointer type;
/// Whether the expression is a constant variable
bool isConstant = false;
/// Whether the expression is pure, i.e. compile-time constant.
bool isPure = false;
/// Whether it is an LValue (i.e. something that can be assigned to).
bool isLValue = false;
/// Whether the expression is used in a context where the LValue is actually required.

12
libsolidity/ast/Types.cpp
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@ -2456,6 +2456,18 @@ u256 FunctionType::externalIdentifier() const
return FixedHash<4>::Arith(FixedHash<4>(dev::keccak256(externalSignature())));
}
bool FunctionType::isPure() const
{
return
m_location == Location::SHA3 ||
m_location == Location::ECRecover ||
m_location == Location::SHA256 ||
m_location == Location::RIPEMD160 ||
m_location == Location::AddMod ||
m_location == Location::MulMod ||
m_location == Location::ObjectCreation;
}
TypePointers FunctionType::parseElementaryTypeVector(strings const& _types)
{
TypePointers pointers;

4
libsolidity/ast/Types.h
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@ -973,6 +973,10 @@ public:
}
bool hasDeclaration() const { return !!m_declaration; }
bool isConstant() const { return m_isConstant; }
/// @returns true if the the result of this function only depends on its arguments
/// and it does not modify the state.
/// Currently, this will only return true for internal functions like keccak and ecrecover.
bool isPure() const;
bool isPayable() const { return m_isPayable; }
/// @return A shared pointer of an ASTString.
/// Can contain a nullptr in which case indicates absence of documentation

53
test/libsolidity/SolidityEndToEndTest.cpp
View File

@ -4542,7 +4542,6 @@ BOOST_AUTO_TEST_CASE(simple_constant_variables_test)
BOOST_AUTO_TEST_CASE(constant_variables)
{
//for now constant specifier is valid only for uint, bytesXX, string and enums
char const* sourceCode = R"(
contract Foo {
uint constant x = 56;
@ -4553,6 +4552,58 @@ BOOST_AUTO_TEST_CASE(constant_variables)
compileAndRun(sourceCode);
}
BOOST_AUTO_TEST_CASE(assignment_to_const_var_involving_expression)
{
char const* sourceCode = R"(
contract C {
uint constant x = 0x123 + 0x456;
function f() returns (uint) { return x + 1; }
}
)";
compileAndRun(sourceCode);
BOOST_CHECK(callContractFunction("f()") == encodeArgs(0x123 + 0x456 + 1));
}
BOOST_AUTO_TEST_CASE(assignment_to_const_var_involving_keccak)
{
char const* sourceCode = R"(
contract C {
bytes32 constant x = keccak256("abc");
function f() returns (bytes32) { return x; }
}
)";
compileAndRun(sourceCode);
BOOST_CHECK(callContractFunction("f()") == encodeArgs(dev::keccak256("abc")));
}
// Disabled until https://github.com/ethereum/solidity/issues/715 is implemented
//BOOST_AUTO_TEST_CASE(assignment_to_const_array_vars)
//{
// char const* sourceCode = R"(
// contract C {
// uint[3] constant x = [uint(1), 2, 3];
// uint constant y = x[0] + x[1] + x[2];
// function f() returns (uint) { return y; }
// }
// )";
// compileAndRun(sourceCode);
// BOOST_CHECK(callContractFunction("f()") == encodeArgs(1 + 2 + 3));
//}
// Disabled until https://github.com/ethereum/solidity/issues/715 is implemented
//BOOST_AUTO_TEST_CASE(constant_struct)
//{
// char const* sourceCode = R"(
// contract C {
// struct S { uint x; uint[] y; }
// S constant x = S(5, new uint[](4));
// function f() returns (uint) { return x.x; }
// }
// )";
// compileAndRun(sourceCode);
// BOOST_CHECK(callContractFunction("f()") == encodeArgs(5));
//}
BOOST_AUTO_TEST_CASE(packed_storage_structs_uint)
{
char const* sourceCode = R"(

90
test/libsolidity/SolidityNameAndTypeResolution.cpp
View File

@ -2173,16 +2173,94 @@ BOOST_AUTO_TEST_CASE(assigning_value_to_const_variable)
CHECK_ERROR(text, TypeError, "");
}
BOOST_AUTO_TEST_CASE(complex_const_variable)
BOOST_AUTO_TEST_CASE(assigning_state_to_const_variable)
{
//for now constant specifier is valid only for uint bytesXX and enums
char const* text = R"(
contract Foo {
mapping(uint => bool) x;
mapping(uint => bool) constant mapVar = x;
contract C {
address constant x = msg.sender;
}
)";
CHECK_ERROR(text, TypeError, "");
// Change to TypeError for 0.5.0.
CHECK_WARNING(text, "Initial value for constant variable has to be compile-time constant.");
}
BOOST_AUTO_TEST_CASE(constant_string_literal_disallows_assignment)
{
char const* text = R"(
contract Test {
string constant x = "abefghijklmnopqabcdefghijklmnopqabcdefghijklmnopqabca";
function f() {
x[0] = "f";
}
}
)";
// Even if this is made possible in the future, we should not allow assignment
// to elements of constant arrays.
CHECK_ERROR(text, TypeError, "Index access for string is not possible.");
}
BOOST_AUTO_TEST_CASE(assign_constant_function_value_to_constant)
{
char const* text = R"(
contract C {
function () constant returns (uint) x;
uint constant y = x();
}
)";
// Change to TypeError for 0.5.0.
CHECK_WARNING(text, "Initial value for constant variable has to be compile-time constant.");
}
BOOST_AUTO_TEST_CASE(assignment_to_const_var_involving_conversion)
{
char const* text = R"(
contract C {
C constant x = C(0x123);
}
)";
CHECK_SUCCESS(text);
}
BOOST_AUTO_TEST_CASE(assignment_to_const_var_involving_expression)
{
char const* text = R"(
contract C {
uint constant x = 0x123 + 0x456;
}
)";
CHECK_SUCCESS(text);
}
BOOST_AUTO_TEST_CASE(assignment_to_const_var_involving_keccak)
{
char const* text = R"(
contract C {
bytes32 constant x = keccak256("abc");
}
)";
CHECK_SUCCESS(text);
}
BOOST_AUTO_TEST_CASE(assignment_to_const_array_vars)
{
char const* text = R"(
contract C {
uint[3] constant x = [uint(1), 2, 3];
}
)";
CHECK_ERROR(text, TypeError, "implemented");
}
BOOST_AUTO_TEST_CASE(constant_struct)
{
char const* text = R"(
contract C {
struct S { uint x; uint[] y; }
S constant x = S(5, new uint[](4));
}
)";
CHECK_ERROR(text, TypeError, "implemented");
}
BOOST_AUTO_TEST_CASE(uninitialized_const_variable)