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Merge pull request #2437 from ethereum/warnDoubleCopyStorage

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Warn about copies in storage that might overwrite unexpectedly.
This commit is contained in:
Alex Beregszaszi 2017-06-27 10:24:03 +01:00 committed by GitHub
commit bc31d4969c
5 changed files with 141 additions and 0 deletions
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1
Changelog.md
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@ -11,6 +11,7 @@ Features:
* Inline Assembly: introduce ``keccak256`` as an opcode. ``sha3`` is still a valid alias.
* Inline Assembly: ``for`` and ``switch`` statements.
* Inline Assembly: function definitions and function calls.
* Type Checker: Warn about copies in storage that might overwrite unexpectedly.
* Code Generator: Added the Whiskers template system.
* Remove obsolete Why3 output.

31
libsolidity/analysis/TypeChecker.cpp
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@ -364,6 +364,35 @@ void TypeChecker::checkLibraryRequirements(ContractDefinition const& _contract)
m_errorReporter.typeError(var->location(), "Library cannot have non-constant state variables");
}
void TypeChecker::checkDoubleStorageAssignment(Assignment const& _assignment)
{
TupleType const& lhs = dynamic_cast<TupleType const&>(*type(_assignment.leftHandSide()));
TupleType const& rhs = dynamic_cast<TupleType const&>(*type(_assignment.rightHandSide()));
bool fillRight = !lhs.components().empty() && (!lhs.components().back() || lhs.components().front());
size_t storageToStorageCopies = 0;
size_t toStorageCopies = 0;
for (size_t i = 0; i < lhs.components().size(); ++i)
{
ReferenceType const* ref = dynamic_cast<ReferenceType const*>(lhs.components()[i].get());
if (!ref || !ref->dataStoredIn(DataLocation::Storage) || ref->isPointer())
continue;
size_t rhsPos = fillRight ? i : rhs.components().size() - (lhs.components().size() - i);
solAssert(rhsPos < rhs.components().size(), "");
toStorageCopies++;
if (rhs.components()[rhsPos]->dataStoredIn(DataLocation::Storage))
storageToStorageCopies++;
}
if (storageToStorageCopies >= 1 && toStorageCopies >= 2)
m_errorReporter.warning(
_assignment.location(),
"This assignment performs two copies to storage. Since storage copies do not first "
"copy to a temporary location, one of them might be overwritten before the second "
"is executed and thus may have unexpected effects. It is safer to perform the copies "
"separately or assign to storage pointers first."
);
}
void TypeChecker::endVisit(InheritanceSpecifier const& _inheritance)
{
auto base = dynamic_cast<ContractDefinition const*>(&dereference(_inheritance.name()));
@ -1047,6 +1076,8 @@ bool TypeChecker::visit(Assignment const& _assignment)
// Sequenced assignments of tuples is not valid, make the result a "void" type.
_assignment.annotation().type = make_shared<TupleType>();
expectType(_assignment.rightHandSide(), *tupleType);
checkDoubleStorageAssignment(_assignment);
}
else if (t->category() == Type::Category::Mapping)
{

3
libsolidity/analysis/TypeChecker.h
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@ -69,6 +69,9 @@ private:
void checkContractExternalTypeClashes(ContractDefinition const& _contract);
/// Checks that all requirements for a library are fulfilled if this is a library.
void checkLibraryRequirements(ContractDefinition const& _contract);
/// Checks (and warns) if a tuple assignment might cause unexpected overwrites in storage.
/// Should only be called if the left hand side is tuple-typed.
void checkDoubleStorageAssignment(Assignment const& _assignment);
virtual void endVisit(InheritanceSpecifier const& _inheritance) override;
virtual void endVisit(UsingForDirective const& _usingFor) override;

32
test/libsolidity/SolidityEndToEndTest.cpp
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@ -4483,6 +4483,38 @@ BOOST_AUTO_TEST_CASE(array_copy_including_mapping)
BOOST_CHECK(storageEmpty(m_contractAddress));
}
BOOST_AUTO_TEST_CASE(swap_in_storage_overwrite)
{
// This tests a swap in storage which does not work as one
// might expect because we do not have temporary storage.
// (x, y) = (y, x) is the same as
// y = x;
// x = y;
char const* sourceCode = R"(
contract c {
struct S { uint a; uint b; }
S public x;
S public y;
function set() {
x.a = 1; x.b = 2;
y.a = 3; y.b = 4;
}
function swap() {
(x, y) = (y, x);
}
}
)";
compileAndRun(sourceCode);
BOOST_CHECK(callContractFunction("x()") == encodeArgs(u256(0), u256(0)));
BOOST_CHECK(callContractFunction("y()") == encodeArgs(u256(0), u256(0)));
BOOST_CHECK(callContractFunction("set()") == encodeArgs());
BOOST_CHECK(callContractFunction("x()") == encodeArgs(u256(1), u256(2)));
BOOST_CHECK(callContractFunction("y()") == encodeArgs(u256(3), u256(4)));
BOOST_CHECK(callContractFunction("swap()") == encodeArgs());
BOOST_CHECK(callContractFunction("x()") == encodeArgs(u256(1), u256(2)));
BOOST_CHECK(callContractFunction("y()") == encodeArgs(u256(1), u256(2)));
}
BOOST_AUTO_TEST_CASE(pass_dynamic_arguments_to_the_base)
{
char const* sourceCode = R"(

74
test/libsolidity/SolidityNameAndTypeResolution.cpp
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@ -5816,6 +5816,80 @@ BOOST_AUTO_TEST_CASE(pure_statement_check_for_regular_for_loop)
success(text);
}
BOOST_AUTO_TEST_CASE(warn_multiple_storage_storage_copies)
{
char const* text = R"(
contract C {
struct S { uint a; uint b; }
S x; S y;
function f() {
(x, y) = (y, x);
}
}
)";
CHECK_WARNING(text, "This assignment performs two copies to storage.");
}
BOOST_AUTO_TEST_CASE(warn_multiple_storage_storage_copies_fill_right)
{
char const* text = R"(
contract C {
struct S { uint a; uint b; }
S x; S y;
function f() {
(x, y, ) = (y, x, 1, 2);
}
}
)";
CHECK_WARNING(text, "This assignment performs two copies to storage.");
}
BOOST_AUTO_TEST_CASE(warn_multiple_storage_storage_copies_fill_left)
{
char const* text = R"(
contract C {
struct S { uint a; uint b; }
S x; S y;
function f() {
(,x, y) = (1, 2, y, x);
}
}
)";
CHECK_WARNING(text, "This assignment performs two copies to storage.");
}
BOOST_AUTO_TEST_CASE(nowarn_swap_memory)
{
char const* text = R"(
contract C {
struct S { uint a; uint b; }
function f() {
S memory x;
S memory y;
(x, y) = (y, x);
}
}
)";
CHECK_SUCCESS_NO_WARNINGS(text);
}
BOOST_AUTO_TEST_CASE(nowarn_swap_storage_pointers)
{
char const* text = R"(
contract C {
struct S { uint a; uint b; }
S x; S y;
function f() {
S storage x_local = x;
S storage y_local = y;
S storage z_local = x;
(x, y_local, x_local, z_local) = (y, x_local, y_local, y);
}
}
)";
CHECK_SUCCESS_NO_WARNINGS(text);
}
BOOST_AUTO_TEST_CASE(warn_unused_local)
{
char const* text = R"(