SmartPtrModeling.cpp
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// SmartPtrModeling.cpp - Model behavior of C++ smart pointers - C++ ------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines a checker that models various aspects of
// C++ smart pointer behavior.
//
//===----------------------------------------------------------------------===//
#include "Move.h"
#include "SmartPtr.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/Type.h"
#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/Checker.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SymExpr.h"
using namespace clang;
using namespace ento;
namespace {
class SmartPtrModeling : public Checker<eval::Call, check::DeadSymbols> {
bool isNullAfterMoveMethod(const CallEvent &Call) const;
public:
// Whether the checker should model for null dereferences of smart pointers.
DefaultBool ModelSmartPtrDereference;
bool evalCall(const CallEvent &Call, CheckerContext &C) const;
void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
void checkDeadSymbols(SymbolReaper &SymReaper, CheckerContext &C) const;
private:
ProgramStateRef updateTrackedRegion(const CallEvent &Call, CheckerContext &C,
const MemRegion *ThisValRegion) const;
void handleReset(const CallEvent &Call, CheckerContext &C) const;
void handleRelease(const CallEvent &Call, CheckerContext &C) const;
void handleSwap(const CallEvent &Call, CheckerContext &C) const;
using SmartPtrMethodHandlerFn =
void (SmartPtrModeling::*)(const CallEvent &Call, CheckerContext &) const;
CallDescriptionMap<SmartPtrMethodHandlerFn> SmartPtrMethodHandlers{
{{"reset"}, &SmartPtrModeling::handleReset},
{{"release"}, &SmartPtrModeling::handleRelease},
{{"swap", 1}, &SmartPtrModeling::handleSwap}};
};
} // end of anonymous namespace
REGISTER_MAP_WITH_PROGRAMSTATE(TrackedRegionMap, const MemRegion *, SVal)
// Define the inter-checker API.
namespace clang {
namespace ento {
namespace smartptr {
bool isStdSmartPtrCall(const CallEvent &Call) {
const auto *MethodDecl = dyn_cast_or_null<CXXMethodDecl>(Call.getDecl());
if (!MethodDecl || !MethodDecl->getParent())
return false;
const auto *RecordDecl = MethodDecl->getParent();
if (!RecordDecl || !RecordDecl->getDeclContext()->isStdNamespace())
return false;
if (RecordDecl->getDeclName().isIdentifier()) {
StringRef Name = RecordDecl->getName();
return Name == "shared_ptr" || Name == "unique_ptr" || Name == "weak_ptr";
}
return false;
}
bool isNullSmartPtr(const ProgramStateRef State, const MemRegion *ThisRegion) {
const auto *InnerPointVal = State->get<TrackedRegionMap>(ThisRegion);
return InnerPointVal && InnerPointVal->isZeroConstant();
}
} // namespace smartptr
} // namespace ento
} // namespace clang
bool SmartPtrModeling::isNullAfterMoveMethod(const CallEvent &Call) const {
// TODO: Update CallDescription to support anonymous calls?
// TODO: Handle other methods, such as .get() or .release().
// But once we do, we'd need a visitor to explain null dereferences
// that are found via such modeling.
const auto *CD = dyn_cast_or_null<CXXConversionDecl>(Call.getDecl());
return CD && CD->getConversionType()->isBooleanType();
}
bool SmartPtrModeling::evalCall(const CallEvent &Call,
CheckerContext &C) const {
if (!smartptr::isStdSmartPtrCall(Call))
return false;
if (isNullAfterMoveMethod(Call)) {
ProgramStateRef State = C.getState();
const MemRegion *ThisR =
cast<CXXInstanceCall>(&Call)->getCXXThisVal().getAsRegion();
if (!move::isMovedFrom(State, ThisR)) {
// TODO: Model this case as well. At least, avoid invalidation of globals.
return false;
}
// TODO: Add a note to bug reports describing this decision.
C.addTransition(
State->BindExpr(Call.getOriginExpr(), C.getLocationContext(),
C.getSValBuilder().makeZeroVal(Call.getResultType())));
return true;
}
if (!ModelSmartPtrDereference)
return false;
if (const auto *CC = dyn_cast<CXXConstructorCall>(&Call)) {
if (CC->getDecl()->isCopyOrMoveConstructor())
return false;
const MemRegion *ThisValRegion = CC->getCXXThisVal().getAsRegion();
if (!ThisValRegion)
return false;
auto State = updateTrackedRegion(Call, C, ThisValRegion);
C.addTransition(State);
return true;
}
const SmartPtrMethodHandlerFn *Handler = SmartPtrMethodHandlers.lookup(Call);
if (!Handler)
return false;
(this->**Handler)(Call, C);
return C.isDifferent();
}
void SmartPtrModeling::checkDeadSymbols(SymbolReaper &SymReaper,
CheckerContext &C) const {
ProgramStateRef State = C.getState();
// Clean up dead regions from the region map.
TrackedRegionMapTy TrackedRegions = State->get<TrackedRegionMap>();
for (auto E : TrackedRegions) {
const MemRegion *Region = E.first;
bool IsRegDead = !SymReaper.isLiveRegion(Region);
if (IsRegDead)
State = State->remove<TrackedRegionMap>(Region);
}
C.addTransition(State);
}
void SmartPtrModeling::handleReset(const CallEvent &Call,
CheckerContext &C) const {
const auto *IC = dyn_cast<CXXInstanceCall>(&Call);
if (!IC)
return;
const MemRegion *ThisValRegion = IC->getCXXThisVal().getAsRegion();
if (!ThisValRegion)
return;
auto State = updateTrackedRegion(Call, C, ThisValRegion);
C.addTransition(State);
// TODO: Make sure to ivalidate the the region in the Store if we don't have
// time to model all methods.
}
void SmartPtrModeling::handleRelease(const CallEvent &Call,
CheckerContext &C) const {
const auto *IC = dyn_cast<CXXInstanceCall>(&Call);
if (!IC)
return;
const MemRegion *ThisValRegion = IC->getCXXThisVal().getAsRegion();
if (!ThisValRegion)
return;
auto State = updateTrackedRegion(Call, C, ThisValRegion);
const auto *InnerPointVal = State->get<TrackedRegionMap>(ThisValRegion);
if (InnerPointVal) {
State = State->BindExpr(Call.getOriginExpr(), C.getLocationContext(),
*InnerPointVal);
}
C.addTransition(State);
// TODO: Add support to enable MallocChecker to start tracking the raw
// pointer.
}
void SmartPtrModeling::handleSwap(const CallEvent &Call,
CheckerContext &C) const {
// TODO: Add support to handle swap method.
}
ProgramStateRef
SmartPtrModeling::updateTrackedRegion(const CallEvent &Call, CheckerContext &C,
const MemRegion *ThisValRegion) const {
// TODO: Refactor and clean up handling too many things.
ProgramStateRef State = C.getState();
auto NumArgs = Call.getNumArgs();
if (NumArgs == 0) {
auto NullSVal = C.getSValBuilder().makeNull();
State = State->set<TrackedRegionMap>(ThisValRegion, NullSVal);
} else if (NumArgs == 1) {
auto ArgVal = Call.getArgSVal(0);
assert(Call.getArgExpr(0)->getType()->isPointerType() &&
"Adding a non pointer value to TrackedRegionMap");
State = State->set<TrackedRegionMap>(ThisValRegion, ArgVal);
}
return State;
}
void ento::registerSmartPtrModeling(CheckerManager &Mgr) {
auto *Checker = Mgr.registerChecker<SmartPtrModeling>();
Checker->ModelSmartPtrDereference =
Mgr.getAnalyzerOptions().getCheckerBooleanOption(
Checker, "ModelSmartPtrDereference");
}
bool ento::shouldRegisterSmartPtrModeling(const CheckerManager &mgr) {
const LangOptions &LO = mgr.getLangOpts();
return LO.CPlusPlus;
}