1 // MisusedMovedObjectChecker.cpp - Check use of moved-from objects. - C++ -===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This defines checker which checks for potential misuses of a moved-from
11 // object. That means method calls on the object or copying it in moved-from
14 //===----------------------------------------------------------------------===//
16 #include "ClangSACheckers.h"
17 #include "clang/AST/ExprCXX.h"
18 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
19 #include "clang/StaticAnalyzer/Core/Checker.h"
20 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
21 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
22 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
24 using namespace clang;
31 enum Kind { Moved, Reported } K;
32 RegionState(Kind InK) : K(InK) {}
35 bool isReported() const { return K == Reported; }
36 bool isMoved() const { return K == Moved; }
38 static RegionState getReported() { return RegionState(Reported); }
39 static RegionState getMoved() { return RegionState(Moved); }
41 bool operator==(const RegionState &X) const { return K == X.K; }
42 void Profile(llvm::FoldingSetNodeID &ID) const { ID.AddInteger(K); }
45 class MisusedMovedObjectChecker
46 : public Checker<check::PreCall, check::PostCall, check::EndFunction,
47 check::DeadSymbols, check::RegionChanges> {
49 void checkEndFunction(CheckerContext &C) const;
50 void checkPreCall(const CallEvent &MC, CheckerContext &C) const;
51 void checkPostCall(const CallEvent &MC, CheckerContext &C) const;
52 void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const;
54 checkRegionChanges(ProgramStateRef State,
55 const InvalidatedSymbols *Invalidated,
56 ArrayRef<const MemRegion *> ExplicitRegions,
57 ArrayRef<const MemRegion *> Regions,
58 const LocationContext *LCtx, const CallEvent *Call) const;
61 class MovedBugVisitor : public BugReporterVisitorImpl<MovedBugVisitor> {
63 MovedBugVisitor(const MemRegion *R) : Region(R), Found(false) {}
65 void Profile(llvm::FoldingSetNodeID &ID) const override {
68 ID.AddPointer(Region);
71 std::shared_ptr<PathDiagnosticPiece> VisitNode(const ExplodedNode *N,
72 const ExplodedNode *PrevN,
73 BugReporterContext &BRC,
74 BugReport &BR) override;
77 // The tracked region.
78 const MemRegion *Region;
82 mutable std::unique_ptr<BugType> BT;
83 ExplodedNode *reportBug(const MemRegion *Region, const CallEvent &Call,
84 CheckerContext &C, bool isCopy) const;
85 bool isInMoveSafeContext(const LocationContext *LC) const;
86 bool isStateResetMethod(const CXXMethodDecl *MethodDec) const;
87 bool isMoveSafeMethod(const CXXMethodDecl *MethodDec) const;
88 const ExplodedNode *getMoveLocation(const ExplodedNode *N,
89 const MemRegion *Region,
90 CheckerContext &C) const;
92 } // end anonymous namespace
94 REGISTER_MAP_WITH_PROGRAMSTATE(TrackedRegionMap, const MemRegion *, RegionState)
96 // If a region is removed all of the subregions needs to be removed too.
97 static ProgramStateRef removeFromState(ProgramStateRef State,
98 const MemRegion *Region) {
101 // Note: The isSubRegionOf function is not reflexive.
102 State = State->remove<TrackedRegionMap>(Region);
103 for (auto &E : State->get<TrackedRegionMap>()) {
104 if (E.first->isSubRegionOf(Region))
105 State = State->remove<TrackedRegionMap>(E.first);
110 static bool isAnyBaseRegionReported(ProgramStateRef State,
111 const MemRegion *Region) {
112 for (auto &E : State->get<TrackedRegionMap>()) {
113 if (Region->isSubRegionOf(E.first) && E.second.isReported())
119 std::shared_ptr<PathDiagnosticPiece>
120 MisusedMovedObjectChecker::MovedBugVisitor::VisitNode(const ExplodedNode *N,
121 const ExplodedNode *PrevN,
122 BugReporterContext &BRC,
124 // We need only the last move of the reported object's region.
125 // The visitor walks the ExplodedGraph backwards.
128 ProgramStateRef State = N->getState();
129 ProgramStateRef StatePrev = PrevN->getState();
130 const RegionState *TrackedObject = State->get<TrackedRegionMap>(Region);
131 const RegionState *TrackedObjectPrev =
132 StatePrev->get<TrackedRegionMap>(Region);
135 if (TrackedObjectPrev && TrackedObject)
138 // Retrieve the associated statement.
139 const Stmt *S = PathDiagnosticLocation::getStmt(N);
144 std::string ObjectName;
145 if (const auto DecReg = Region->getAs<DeclRegion>()) {
146 const auto *RegionDecl = dyn_cast<NamedDecl>(DecReg->getDecl());
147 ObjectName = RegionDecl->getNameAsString();
149 std::string InfoText;
150 if (ObjectName != "")
151 InfoText = "'" + ObjectName + "' became 'moved-from' here";
153 InfoText = "Became 'moved-from' here";
155 // Generate the extra diagnostic.
156 PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
157 N->getLocationContext());
158 return std::make_shared<PathDiagnosticEventPiece>(Pos, InfoText, true);
161 const ExplodedNode *MisusedMovedObjectChecker::getMoveLocation(
162 const ExplodedNode *N, const MemRegion *Region, CheckerContext &C) const {
163 // Walk the ExplodedGraph backwards and find the first node that referred to
164 // the tracked region.
165 const ExplodedNode *MoveNode = N;
168 ProgramStateRef State = N->getState();
169 if (!State->get<TrackedRegionMap>(Region))
172 N = N->pred_empty() ? nullptr : *(N->pred_begin());
177 ExplodedNode *MisusedMovedObjectChecker::reportBug(const MemRegion *Region,
178 const CallEvent &Call,
180 bool isCopy = false) const {
181 if (ExplodedNode *N = C.generateNonFatalErrorNode()) {
183 BT.reset(new BugType(this, "Usage of a 'moved-from' object",
184 "C++ move semantics"));
186 // Uniqueing report to the same object.
187 PathDiagnosticLocation LocUsedForUniqueing;
188 const ExplodedNode *MoveNode = getMoveLocation(N, Region, C);
190 if (const Stmt *MoveStmt = PathDiagnosticLocation::getStmt(MoveNode))
191 LocUsedForUniqueing = PathDiagnosticLocation::createBegin(
192 MoveStmt, C.getSourceManager(), MoveNode->getLocationContext());
194 // Creating the error message.
195 std::string ErrorMessage;
197 ErrorMessage = "Copying a 'moved-from' object";
199 ErrorMessage = "Method call on a 'moved-from' object";
200 if (const auto DecReg = Region->getAs<DeclRegion>()) {
201 const auto *RegionDecl = dyn_cast<NamedDecl>(DecReg->getDecl());
202 ErrorMessage += " '" + RegionDecl->getNameAsString() + "'";
206 llvm::make_unique<BugReport>(*BT, ErrorMessage, N, LocUsedForUniqueing,
207 MoveNode->getLocationContext()->getDecl());
208 R->addVisitor(llvm::make_unique<MovedBugVisitor>(Region));
209 C.emitReport(std::move(R));
215 // Removing the function parameters' MemRegion from the state. This is needed
216 // for PODs where the trivial destructor does not even created nor executed.
217 void MisusedMovedObjectChecker::checkEndFunction(CheckerContext &C) const {
218 auto State = C.getState();
219 TrackedRegionMapTy Objects = State->get<TrackedRegionMap>();
220 if (Objects.isEmpty())
223 auto LC = C.getLocationContext();
225 const auto LD = dyn_cast_or_null<FunctionDecl>(LC->getDecl());
228 llvm::SmallSet<const MemRegion *, 8> InvalidRegions;
230 for (auto Param : LD->parameters()) {
231 auto Type = Param->getType().getTypePtrOrNull();
234 if (!Type->isPointerType() && !Type->isReferenceType()) {
235 InvalidRegions.insert(State->getLValue(Param, LC).getAsRegion());
239 if (InvalidRegions.empty())
242 for (const auto &E : State->get<TrackedRegionMap>()) {
243 if (InvalidRegions.count(E.first->getBaseRegion()))
244 State = State->remove<TrackedRegionMap>(E.first);
247 C.addTransition(State);
250 void MisusedMovedObjectChecker::checkPostCall(const CallEvent &Call,
251 CheckerContext &C) const {
252 const auto *AFC = dyn_cast<AnyFunctionCall>(&Call);
256 ProgramStateRef State = C.getState();
257 const auto MethodDecl = dyn_cast_or_null<CXXMethodDecl>(AFC->getDecl());
261 const auto *ConstructorDecl = dyn_cast<CXXConstructorDecl>(MethodDecl);
263 const auto *CC = dyn_cast_or_null<CXXConstructorCall>(&Call);
264 // Check if an object became moved-from.
265 // Object can become moved from after a call to move assignment operator or
266 // move constructor .
267 if (ConstructorDecl && !ConstructorDecl->isMoveConstructor())
270 if (!ConstructorDecl && !MethodDecl->isMoveAssignmentOperator())
273 const auto ArgRegion = AFC->getArgSVal(0).getAsRegion();
277 // Skip moving the object to itself.
278 if (CC && CC->getCXXThisVal().getAsRegion() == ArgRegion)
280 if (const auto *IC = dyn_cast<CXXInstanceCall>(AFC))
281 if (IC->getCXXThisVal().getAsRegion() == ArgRegion)
284 const MemRegion *BaseRegion = ArgRegion->getBaseRegion();
285 // Skip temp objects because of their short lifetime.
286 if (BaseRegion->getAs<CXXTempObjectRegion>() ||
287 AFC->getArgExpr(0)->isRValue())
289 // If it has already been reported do not need to modify the state.
291 if (State->get<TrackedRegionMap>(ArgRegion))
293 // Mark object as moved-from.
294 State = State->set<TrackedRegionMap>(ArgRegion, RegionState::getMoved());
295 C.addTransition(State);
298 bool MisusedMovedObjectChecker::isMoveSafeMethod(
299 const CXXMethodDecl *MethodDec) const {
300 // We abandon the cases where bool/void/void* conversion happens.
301 if (const auto *ConversionDec =
302 dyn_cast_or_null<CXXConversionDecl>(MethodDec)) {
303 const Type *Tp = ConversionDec->getConversionType().getTypePtrOrNull();
306 if (Tp->isBooleanType() || Tp->isVoidType() || Tp->isVoidPointerType())
309 // Function call `empty` can be skipped.
310 if (MethodDec && MethodDec->getDeclName().isIdentifier() &&
311 (MethodDec->getName().lower() == "empty" ||
312 MethodDec->getName().lower() == "isempty"))
318 bool MisusedMovedObjectChecker::isStateResetMethod(
319 const CXXMethodDecl *MethodDec) const {
320 if (MethodDec && MethodDec->getDeclName().isIdentifier()) {
321 std::string MethodName = MethodDec->getName().lower();
322 if (MethodName == "reset" || MethodName == "clear" ||
323 MethodName == "destroy")
329 // Don't report an error inside a move related operation.
330 // We assume that the programmer knows what she does.
331 bool MisusedMovedObjectChecker::isInMoveSafeContext(
332 const LocationContext *LC) const {
334 const auto *CtxDec = LC->getDecl();
335 auto *CtorDec = dyn_cast_or_null<CXXConstructorDecl>(CtxDec);
336 auto *DtorDec = dyn_cast_or_null<CXXDestructorDecl>(CtxDec);
337 auto *MethodDec = dyn_cast_or_null<CXXMethodDecl>(CtxDec);
338 if (DtorDec || (CtorDec && CtorDec->isCopyOrMoveConstructor()) ||
339 (MethodDec && MethodDec->isOverloadedOperator() &&
340 MethodDec->getOverloadedOperator() == OO_Equal) ||
341 isStateResetMethod(MethodDec) || isMoveSafeMethod(MethodDec))
343 } while ((LC = LC->getParent()));
347 void MisusedMovedObjectChecker::checkPreCall(const CallEvent &Call,
348 CheckerContext &C) const {
349 ProgramStateRef State = C.getState();
350 const LocationContext *LC = C.getLocationContext();
351 ExplodedNode *N = nullptr;
353 // Remove the MemRegions from the map on which a ctor/dtor call or assignement
356 // Checking constructor calls.
357 if (const auto *CC = dyn_cast<CXXConstructorCall>(&Call)) {
358 State = removeFromState(State, CC->getCXXThisVal().getAsRegion());
359 auto CtorDec = CC->getDecl();
360 // Check for copying a moved-from object and report the bug.
361 if (CtorDec && CtorDec->isCopyOrMoveConstructor()) {
362 const MemRegion *ArgRegion = CC->getArgSVal(0).getAsRegion();
363 const RegionState *ArgState = State->get<TrackedRegionMap>(ArgRegion);
364 if (ArgState && ArgState->isMoved()) {
365 if (!isInMoveSafeContext(LC)) {
366 N = reportBug(ArgRegion, Call, C, /*isCopy=*/true);
367 State = State->set<TrackedRegionMap>(ArgRegion,
368 RegionState::getReported());
372 C.addTransition(State, N);
376 const auto IC = dyn_cast<CXXInstanceCall>(&Call);
379 // In case of destructor call we do not track the object anymore.
380 const MemRegion *ThisRegion = IC->getCXXThisVal().getAsRegion();
381 if (dyn_cast_or_null<CXXDestructorDecl>(Call.getDecl())) {
382 State = removeFromState(State, IC->getCXXThisVal().getAsRegion());
383 C.addTransition(State);
387 const auto MethodDecl = dyn_cast_or_null<CXXMethodDecl>(IC->getDecl());
390 // Checking assignment operators.
391 bool OperatorEq = MethodDecl->isOverloadedOperator() &&
392 MethodDecl->getOverloadedOperator() == OO_Equal;
393 // Remove the tracked object for every assignment operator, but report bug
394 // only for move or copy assignment's argument.
396 State = removeFromState(State, ThisRegion);
397 if (MethodDecl->isCopyAssignmentOperator() ||
398 MethodDecl->isMoveAssignmentOperator()) {
399 const RegionState *ArgState =
400 State->get<TrackedRegionMap>(IC->getArgSVal(0).getAsRegion());
401 if (ArgState && ArgState->isMoved() && !isInMoveSafeContext(LC)) {
402 const MemRegion *ArgRegion = IC->getArgSVal(0).getAsRegion();
403 N = reportBug(ArgRegion, Call, C, /*isCopy=*/true);
405 State->set<TrackedRegionMap>(ArgRegion, RegionState::getReported());
408 C.addTransition(State, N);
412 // The remaining part is check only for method call on a moved-from object.
413 if (isMoveSafeMethod(MethodDecl))
416 if (isStateResetMethod(MethodDecl)) {
417 State = State->remove<TrackedRegionMap>(ThisRegion);
418 C.addTransition(State);
422 // If it is already reported then we dont report the bug again.
423 const RegionState *ThisState = State->get<TrackedRegionMap>(ThisRegion);
424 if (!(ThisState && ThisState->isMoved()))
427 // Dont report it in case if any base region is already reported
428 if (isAnyBaseRegionReported(State, ThisRegion))
431 if (isInMoveSafeContext(LC))
434 N = reportBug(ThisRegion, Call, C);
435 State = State->set<TrackedRegionMap>(ThisRegion, RegionState::getReported());
436 C.addTransition(State, N);
439 void MisusedMovedObjectChecker::checkDeadSymbols(SymbolReaper &SymReaper,
440 CheckerContext &C) const {
441 ProgramStateRef State = C.getState();
442 TrackedRegionMapTy TrackedRegions = State->get<TrackedRegionMap>();
443 for (TrackedRegionMapTy::value_type E : TrackedRegions) {
444 const MemRegion *Region = E.first;
445 bool IsRegDead = !SymReaper.isLiveRegion(Region);
447 // Remove the dead regions from the region map.
449 State = State->remove<TrackedRegionMap>(Region);
452 C.addTransition(State);
455 ProgramStateRef MisusedMovedObjectChecker::checkRegionChanges(
456 ProgramStateRef State, const InvalidatedSymbols *Invalidated,
457 ArrayRef<const MemRegion *> ExplicitRegions,
458 ArrayRef<const MemRegion *> Regions, const LocationContext *LCtx,
459 const CallEvent *Call) const {
460 // In case of an InstanceCall don't remove the ThisRegion from the GDM since
461 // it is handled in checkPreCall and checkPostCall.
462 const MemRegion *ThisRegion = nullptr;
463 if (const auto *IC = dyn_cast_or_null<CXXInstanceCall>(Call)) {
464 ThisRegion = IC->getCXXThisVal().getAsRegion();
467 for (ArrayRef<const MemRegion *>::iterator I = ExplicitRegions.begin(),
468 E = ExplicitRegions.end();
470 const auto *Region = *I;
471 if (ThisRegion != Region) {
472 State = removeFromState(State, Region);
479 void ento::registerMisusedMovedObjectChecker(CheckerManager &mgr) {
480 mgr.registerChecker<MisusedMovedObjectChecker>();