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/*
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/>.
*/
#include <libsolidity/analysis/ControlFlowAnalyzer.h>
using namespace std;
using namespace dev::solidity;
bool ControlFlowAnalyzer::analyze(ASTNode const& _astRoot)
{
_astRoot.accept(*this);
return Error::containsOnlyWarnings(m_errorReporter.errors());
}
bool ControlFlowAnalyzer::visit(FunctionDefinition const& _function)
{
auto const& functionFlow = m_cfg.functionFlow(_function);
checkUnassignedStorageReturnValues(_function, functionFlow.entry, functionFlow.exit);
return false;
}
set<VariableDeclaration const*> ControlFlowAnalyzer::variablesAssignedInNode(CFGNode const *node)
{
set<VariableDeclaration const*> result;
for (auto expression: node->block.expressions)
{
if (auto const* assignment = dynamic_cast<Assignment const*>(expression))
{
stack<Expression const*> expressions;
expressions.push(&assignment->leftHandSide());
while (!expressions.empty())
{
Expression const* expression = expressions.top();
expressions.pop();
if (auto const *tuple = dynamic_cast<TupleExpression const*>(expression))
for (auto const& component: tuple->components())
expressions.push(component.get());
else if (auto const* identifier = dynamic_cast<Identifier const*>(expression))
if (auto const* variableDeclaration = dynamic_cast<VariableDeclaration const*>(
identifier->annotation().referencedDeclaration
))
result.insert(variableDeclaration);
}
}
}
return result;
}
void ControlFlowAnalyzer::checkUnassignedStorageReturnValues(
FunctionDefinition const& _function,
CFGNode const* _functionEntry,
CFGNode const* _functionExit
) const
{
if (_function.returnParameterList()->parameters().empty())
return;
map<CFGNode const*, set<VariableDeclaration const*>> unassigned;
{
auto& unassignedAtFunctionEntry = unassigned[_functionEntry];
for (auto const& returnParameter: _function.returnParameterList()->parameters())
if (returnParameter->type()->dataStoredIn(DataLocation::Storage))
unassignedAtFunctionEntry.insert(returnParameter.get());
}
stack<CFGNode const*> nodesToTraverse;
nodesToTraverse.push(_functionEntry);
// walk all paths from entry with maximal set of unassigned return values
while (!nodesToTraverse.empty())
{
auto node = nodesToTraverse.top();
nodesToTraverse.pop();
auto& unassignedAtNode = unassigned[node];
if (node->block.returnStatement != nullptr)
if (node->block.returnStatement->expression())
unassignedAtNode.clear();
if (!unassignedAtNode.empty())
{
// kill all return values to which a value is assigned
for (auto const* variableDeclaration: variablesAssignedInNode(node))
unassignedAtNode.erase(variableDeclaration);
// kill all return values referenced in inline assembly
// a reference is enough, checking whether there actually was an assignment might be overkill
for (auto assembly: node->block.inlineAssemblyStatements)
for (auto const& ref: assembly->annotation().externalReferences)
if (auto variableDeclaration = dynamic_cast<VariableDeclaration const*>(ref.second.declaration))
unassignedAtNode.erase(variableDeclaration);
}
for (auto const& exit: node->exits)
{
auto& unassignedAtExit = unassigned[exit];
auto oldSize = unassignedAtExit.size();
unassignedAtExit.insert(unassignedAtNode.begin(), unassignedAtNode.end());
// (re)traverse an exit, if we are on a path with new unassigned return values to consider
// this will terminate, since there is only a finite number of unassigned return values
if (unassignedAtExit.size() > oldSize)
nodesToTraverse.push(exit);
}
}
if (!unassigned[_functionExit].empty())
{
vector<VariableDeclaration const*> unassignedOrdered(
unassigned[_functionExit].begin(),
unassigned[_functionExit].end()
);
sort(
unassignedOrdered.begin(),
unassignedOrdered.end(),
[](VariableDeclaration const* lhs, VariableDeclaration const* rhs) -> bool {
return lhs->id() < rhs->id();
}
);
for (auto const* returnVal: unassignedOrdered)
{
SecondarySourceLocation ssl;
for (CFGNode* lastNodeBeforeExit: _functionExit->entries)
if (unassigned[lastNodeBeforeExit].count(returnVal))
{
if (!!lastNodeBeforeExit->block.returnStatement)
ssl.append("Problematic return:", lastNodeBeforeExit->block.returnStatement->location());
else
ssl.append("Problematic end of function:", _function.location());
}
m_errorReporter.warning(
returnVal->location(),
"This variable is of storage pointer type and might be returned without assignment. "
"This can cause storage corruption. Assign the variable (potentially from itself) "
"to remove this warning.",
ssl
);
}
}
}
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