clang/lib/StaticAnalyzer/Checkers/MoveChecker.cpp

   1 // MoveChecker.cpp - Check use of moved-from objects. - C++ ---------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This defines checker which checks for potential misuses of a moved-from
  10 // object. That means method calls on the object or copying it in moved-from
  11 // state.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "clang/AST/Attr.h"
  16 #include "clang/AST/ExprCXX.h"
  17 #include "clang/Driver/DriverDiagnostic.h"
  18 #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
  19 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
  20 #include "clang/StaticAnalyzer/Core/Checker.h"
  21 #include "clang/StaticAnalyzer/Core/CheckerManager.h"
  22 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
  23 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
  24 #include "llvm/ADT/StringSet.h"
  25
  26 using namespace clang;
  27 using namespace ento;
  28
  29 namespace {
  30 struct RegionState {
  31 private:
  32   enum Kind { Moved, Reported } K;
  33   RegionState(Kind InK) : K(InK) {}
  34
  35 public:
  36   bool isReported() const { return K == Reported; }
  37   bool isMoved() const { return K == Moved; }
  38
  39   static RegionState getReported() { return RegionState(Reported); }
  40   static RegionState getMoved() { return RegionState(Moved); }
  41
  42   bool operator==(const RegionState &X) const { return K == X.K; }
  43   void Profile(llvm::FoldingSetNodeID &ID) const { ID.AddInteger(K); }
  44 };
  45 } // end of anonymous namespace
  46
  47 namespace {
  48 class MoveChecker
  49     : public Checker<check::PreCall, check::PostCall,
  50                      check::DeadSymbols, check::RegionChanges> {
  51 public:
  52   void checkPreCall(const CallEvent &MC, CheckerContext &C) const;
  53   void checkPostCall(const CallEvent &MC, CheckerContext &C) const;
  54   void checkDeadSymbols(SymbolReaper &SR, CheckerContext &C) const;
  55   ProgramStateRef
  56   checkRegionChanges(ProgramStateRef State,
  57                      const InvalidatedSymbols *Invalidated,
  58                      ArrayRef<const MemRegion *> RequestedRegions,
  59                      ArrayRef<const MemRegion *> InvalidatedRegions,
  60                      const LocationContext *LCtx, const CallEvent *Call) const;
  61   void printState(raw_ostream &Out, ProgramStateRef State,
  62                   const char *NL, const char *Sep) const override;
  63
  64 private:
  65   enum MisuseKind { MK_FunCall, MK_Copy, MK_Move, MK_Dereference };
  66   enum StdObjectKind { SK_NonStd, SK_Unsafe, SK_Safe, SK_SmartPtr };
  67
  68   enum AggressivenessKind { // In any case, don't warn after a reset.
  69     AK_Invalid = -1,
  70     AK_KnownsOnly = 0,      // Warn only about known move-unsafe classes.
  71     AK_KnownsAndLocals = 1, // Also warn about all local objects.
  72     AK_All = 2,             // Warn on any use-after-move.
  73     AK_NumKinds = AK_All
  74   };
  75
  76   static bool misuseCausesCrash(MisuseKind MK) {
  77     return MK == MK_Dereference;
  78   }
  79
  80   struct ObjectKind {
  81     // Is this a local variable or a local rvalue reference?
  82     bool IsLocal;
  83     // Is this an STL object? If so, of what kind?
  84     StdObjectKind StdKind;
  85   };
  86
  87   // STL smart pointers are automatically re-initialized to null when moved
  88   // from. So we can't warn on many methods, but we can warn when it is
  89   // dereferenced, which is UB even if the resulting lvalue never gets read.
  90   const llvm::StringSet<> StdSmartPtrClasses = {
  91       "shared_ptr",
  92       "unique_ptr",
  93       "weak_ptr",
  94   };
  95
  96   // Not all of these are entirely move-safe, but they do provide *some*
  97   // guarantees, and it means that somebody is using them after move
  98   // in a valid manner.
  99   // TODO: We can still try to identify *unsafe* use after move,
 100   // like we did with smart pointers.
 101   const llvm::StringSet<> StdSafeClasses = {
 102       "basic_filebuf",
 103       "basic_ios",
 104       "future",
 105       "optional",
 106       "packaged_task",
 107       "promise",
 108       "shared_future",
 109       "shared_lock",
 110       "thread",
 111       "unique_lock",
 112   };
 113
 114   // Should we bother tracking the state of the object?
 115   bool shouldBeTracked(ObjectKind OK) const {
 116     // In non-aggressive mode, only warn on use-after-move of local variables
 117     // (or local rvalue references) and of STL objects. The former is possible
 118     // because local variables (or local rvalue references) are not tempting
 119     // their user to re-use the storage. The latter is possible because STL
 120     // objects are known to end up in a valid but unspecified state after the
 121     // move and their state-reset methods are also known, which allows us to
 122     // predict precisely when use-after-move is invalid.
 123     // Some STL objects are known to conform to additional contracts after move,
 124     // so they are not tracked. However, smart pointers specifically are tracked
 125     // because we can perform extra checking over them.
 126     // In aggressive mode, warn on any use-after-move because the user has
 127     // intentionally asked us to completely eliminate use-after-move
 128     // in his code.
 129     return (Aggressiveness == AK_All) ||
 130            (Aggressiveness >= AK_KnownsAndLocals && OK.IsLocal) ||
 131            OK.StdKind == SK_Unsafe || OK.StdKind == SK_SmartPtr;
 132   }
 133
 134   // Some objects only suffer from some kinds of misuses, but we need to track
 135   // them anyway because we cannot know in advance what misuse will we find.
 136   bool shouldWarnAbout(ObjectKind OK, MisuseKind MK) const {
 137     // Additionally, only warn on smart pointers when they are dereferenced (or
 138     // local or we are aggressive).
 139     return shouldBeTracked(OK) &&
 140            ((Aggressiveness == AK_All) ||
 141             (Aggressiveness >= AK_KnownsAndLocals && OK.IsLocal) ||
 142             OK.StdKind != SK_SmartPtr || MK == MK_Dereference);
 143   }
 144
 145   // Obtains ObjectKind of an object. Because class declaration cannot always
 146   // be easily obtained from the memory region, it is supplied separately.
 147   ObjectKind classifyObject(const MemRegion *MR, const CXXRecordDecl *RD) const;
 148
 149   // Classifies the object and dumps a user-friendly description string to
 150   // the stream.
 151   void explainObject(llvm::raw_ostream &OS, const MemRegion *MR,
 152                      const CXXRecordDecl *RD, MisuseKind MK) const;
 153
 154   bool belongsTo(const CXXRecordDecl *RD, const llvm::StringSet<> &Set) const;
 155
 156   class MovedBugVisitor : public BugReporterVisitor {
 157   public:
 158     MovedBugVisitor(const MoveChecker &Chk, const MemRegion *R,
 159                     const CXXRecordDecl *RD, MisuseKind MK)
 160         : Chk(Chk), Region(R), RD(RD), MK(MK), Found(false) {}
 161
 162     void Profile(llvm::FoldingSetNodeID &ID) const override {
 163       static int X = 0;
 164       ID.AddPointer(&X);
 165       ID.AddPointer(Region);
 166       // Don't add RD because it's, in theory, uniquely determined by
 167       // the region. In practice though, it's not always possible to obtain
 168       // the declaration directly from the region, that's why we store it
 169       // in the first place.
 170     }
 171
 172     PathDiagnosticPieceRef VisitNode(const ExplodedNode *N,
 173                                      BugReporterContext &BRC,
 174                                      PathSensitiveBugReport &BR) override;
 175
 176   private:
 177     const MoveChecker &Chk;
 178     // The tracked region.
 179     const MemRegion *Region;
 180     // The class of the tracked object.
 181     const CXXRecordDecl *RD;
 182     // How exactly the object was misused.
 183     const MisuseKind MK;
 184     bool Found;
 185   };
 186
 187   AggressivenessKind Aggressiveness = AK_KnownsAndLocals;
 188
 189 public:
 190   void setAggressiveness(StringRef Str, CheckerManager &Mgr) {
 191     Aggressiveness =
 192         llvm::StringSwitch<AggressivenessKind>(Str)
 193             .Case("KnownsOnly", AK_KnownsOnly)
 194             .Case("KnownsAndLocals", AK_KnownsAndLocals)
 195             .Case("All", AK_All)
 196             .Default(AK_Invalid);
 197
 198     if (Aggressiveness == AK_Invalid)
 199       Mgr.reportInvalidCheckerOptionValue(this, "WarnOn",
 200           "either \"KnownsOnly\", \"KnownsAndLocals\" or \"All\" string value");
 201   };
 202
 203 private:
 204   BugType BT{this, "Use-after-move", categories::CXXMoveSemantics};
 205
 206   // Check if the given form of potential misuse of a given object
 207   // should be reported. If so, get it reported. The callback from which
 208   // this function was called should immediately return after the call
 209   // because this function adds one or two transitions.
 210   void modelUse(ProgramStateRef State, const MemRegion *Region,
 211                 const CXXRecordDecl *RD, MisuseKind MK,
 212                 CheckerContext &C) const;
 213
 214   // Returns the exploded node against which the report was emitted.
 215   // The caller *must* add any further transitions against this node.
 216   // Returns nullptr and does not report if such node already exists.
 217   ExplodedNode *tryToReportBug(const MemRegion *Region, const CXXRecordDecl *RD,
 218                                CheckerContext &C, MisuseKind MK) const;
 219
 220   bool isInMoveSafeContext(const LocationContext *LC) const;
 221   bool isStateResetMethod(const CXXMethodDecl *MethodDec) const;
 222   bool isMoveSafeMethod(const CXXMethodDecl *MethodDec) const;
 223   const ExplodedNode *getMoveLocation(const ExplodedNode *N,
 224                                       const MemRegion *Region,
 225                                       CheckerContext &C) const;
 226 };
 227 } // end anonymous namespace
 228
 229 REGISTER_MAP_WITH_PROGRAMSTATE(TrackedRegionMap, const MemRegion *, RegionState)
 230
 231 // Define the inter-checker API.
 232 namespace clang {
 233 namespace ento {
 234 namespace move {
 235 bool isMovedFrom(ProgramStateRef State, const MemRegion *Region) {
 236   const RegionState *RS = State->get<TrackedRegionMap>(Region);
 237   return RS && (RS->isMoved() || RS->isReported());
 238 }
 239 } // namespace move
 240 } // namespace ento
 241 } // namespace clang
 242
 243 // If a region is removed all of the subregions needs to be removed too.
 244 static ProgramStateRef removeFromState(ProgramStateRef State,
 245                                        const MemRegion *Region) {
 246   if (!Region)
 247     return State;
 248   for (auto &E : State->get<TrackedRegionMap>()) {
 249     if (E.first->isSubRegionOf(Region))
 250       State = State->remove<TrackedRegionMap>(E.first);
 251   }
 252   return State;
 253 }
 254
 255 static bool isAnyBaseRegionReported(ProgramStateRef State,
 256                                     const MemRegion *Region) {
 257   for (auto &E : State->get<TrackedRegionMap>()) {
 258     if (Region->isSubRegionOf(E.first) && E.second.isReported())
 259       return true;
 260   }
 261   return false;
 262 }
 263
 264 static const MemRegion *unwrapRValueReferenceIndirection(const MemRegion *MR) {
 265   if (const auto *SR = dyn_cast_or_null<SymbolicRegion>(MR)) {
 266     SymbolRef Sym = SR->getSymbol();
 267     if (Sym->getType()->isRValueReferenceType())
 268       if (const MemRegion *OriginMR = Sym->getOriginRegion())
 269         return OriginMR;
 270   }
 271   return MR;
 272 }
 273
 274 PathDiagnosticPieceRef
 275 MoveChecker::MovedBugVisitor::VisitNode(const ExplodedNode *N,
 276                                         BugReporterContext &BRC,
 277                                         PathSensitiveBugReport &BR) {
 278   // We need only the last move of the reported object's region.
 279   // The visitor walks the ExplodedGraph backwards.
 280   if (Found)
 281     return nullptr;
 282   ProgramStateRef State = N->getState();
 283   ProgramStateRef StatePrev = N->getFirstPred()->getState();
 284   const RegionState *TrackedObject = State->get<TrackedRegionMap>(Region);
 285   const RegionState *TrackedObjectPrev =
 286       StatePrev->get<TrackedRegionMap>(Region);
 287   if (!TrackedObject)
 288     return nullptr;
 289   if (TrackedObjectPrev && TrackedObject)
 290     return nullptr;
 291
 292   // Retrieve the associated statement.
 293   const Stmt *S = N->getStmtForDiagnostics();
 294   if (!S)
 295     return nullptr;
 296   Found = true;
 297
 298   SmallString<128> Str;
 299   llvm::raw_svector_ostream OS(Str);
 300
 301   ObjectKind OK = Chk.classifyObject(Region, RD);
 302   switch (OK.StdKind) {
 303     case SK_SmartPtr:
 304       if (MK == MK_Dereference) {
 305         OS << "Smart pointer";
 306         Chk.explainObject(OS, Region, RD, MK);
 307         OS << " is reset to null when moved from";
 308         break;
 309       }
 310
 311       // If it's not a dereference, we don't care if it was reset to null
 312       // or that it is even a smart pointer.
 313       [[fallthrough]];
 314     case SK_NonStd:
 315     case SK_Safe:
 316       OS << "Object";
 317       Chk.explainObject(OS, Region, RD, MK);
 318       OS << " is moved";
 319       break;
 320     case SK_Unsafe:
 321       OS << "Object";
 322       Chk.explainObject(OS, Region, RD, MK);
 323       OS << " is left in a valid but unspecified state after move";
 324       break;
 325   }
 326
 327   // Generate the extra diagnostic.
 328   PathDiagnosticLocation Pos(S, BRC.getSourceManager(),
 329                              N->getLocationContext());
 330   return std::make_shared<PathDiagnosticEventPiece>(Pos, OS.str(), true);
 331 }
 332
 333 const ExplodedNode *MoveChecker::getMoveLocation(const ExplodedNode *N,
 334                                                  const MemRegion *Region,
 335                                                  CheckerContext &C) const {
 336   // Walk the ExplodedGraph backwards and find the first node that referred to
 337   // the tracked region.
 338   const ExplodedNode *MoveNode = N;
 339
 340   while (N) {
 341     ProgramStateRef State = N->getState();
 342     if (!State->get<TrackedRegionMap>(Region))
 343       break;
 344     MoveNode = N;
 345     N = N->pred_empty() ? nullptr : *(N->pred_begin());
 346   }
 347   return MoveNode;
 348 }
 349
 350 void MoveChecker::modelUse(ProgramStateRef State, const MemRegion *Region,
 351                            const CXXRecordDecl *RD, MisuseKind MK,
 352                            CheckerContext &C) const {
 353   assert(!C.isDifferent() && "No transitions should have been made by now");
 354   const RegionState *RS = State->get<TrackedRegionMap>(Region);
 355   ObjectKind OK = classifyObject(Region, RD);
 356
 357   // Just in case: if it's not a smart pointer but it does have operator *,
 358   // we shouldn't call the bug a dereference.
 359   if (MK == MK_Dereference && OK.StdKind != SK_SmartPtr)
 360     MK = MK_FunCall;
 361
 362   if (!RS || !shouldWarnAbout(OK, MK)
 363           || isInMoveSafeContext(C.getLocationContext())) {
 364     // Finalize changes made by the caller.
 365     C.addTransition(State);
 366     return;
 367   }
 368
 369   // Don't report it in case if any base region is already reported.
 370   // But still generate a sink in case of UB.
 371   // And still finalize changes made by the caller.
 372   if (isAnyBaseRegionReported(State, Region)) {
 373     if (misuseCausesCrash(MK)) {
 374       C.generateSink(State, C.getPredecessor());
 375     } else {
 376       C.addTransition(State);
 377     }
 378     return;
 379   }
 380
 381   ExplodedNode *N = tryToReportBug(Region, RD, C, MK);
 382
 383   // If the program has already crashed on this path, don't bother.
 384   if (!N || N->isSink())
 385     return;
 386
 387   State = State->set<TrackedRegionMap>(Region, RegionState::getReported());
 388   C.addTransition(State, N);
 389 }
 390
 391 ExplodedNode *MoveChecker::tryToReportBug(const MemRegion *Region,
 392                                           const CXXRecordDecl *RD,
 393                                           CheckerContext &C,
 394                                           MisuseKind MK) const {
 395   if (ExplodedNode *N = misuseCausesCrash(MK) ? C.generateErrorNode()
 396                                               : C.generateNonFatalErrorNode()) {
 397     // Uniqueing report to the same object.
 398     PathDiagnosticLocation LocUsedForUniqueing;
 399     const ExplodedNode *MoveNode = getMoveLocation(N, Region, C);
 400
 401     if (const Stmt *MoveStmt = MoveNode->getStmtForDiagnostics())
 402       LocUsedForUniqueing = PathDiagnosticLocation::createBegin(
 403           MoveStmt, C.getSourceManager(), MoveNode->getLocationContext());
 404
 405     // Creating the error message.
 406     llvm::SmallString<128> Str;
 407     llvm::raw_svector_ostream OS(Str);
 408     switch(MK) {
 409       case MK_FunCall:
 410         OS << "Method called on moved-from object";
 411         explainObject(OS, Region, RD, MK);
 412         break;
 413       case MK_Copy:
 414         OS << "Moved-from object";
 415         explainObject(OS, Region, RD, MK);
 416         OS << " is copied";
 417         break;
 418       case MK_Move:
 419         OS << "Moved-from object";
 420         explainObject(OS, Region, RD, MK);
 421         OS << " is moved";
 422         break;
 423       case MK_Dereference:
 424         OS << "Dereference of null smart pointer";
 425         explainObject(OS, Region, RD, MK);
 426         break;
 427     }
 428
 429     auto R = std::make_unique<PathSensitiveBugReport>(
 430         BT, OS.str(), N, LocUsedForUniqueing,
 431         MoveNode->getLocationContext()->getDecl());
 432     R->addVisitor(std::make_unique<MovedBugVisitor>(*this, Region, RD, MK));
 433     C.emitReport(std::move(R));
 434     return N;
 435   }
 436   return nullptr;
 437 }
 438
 439 void MoveChecker::checkPostCall(const CallEvent &Call,
 440                                 CheckerContext &C) const {
 441   const auto *AFC = dyn_cast<AnyFunctionCall>(&Call);
 442   if (!AFC)
 443     return;
 444
 445   ProgramStateRef State = C.getState();
 446   const auto MethodDecl = dyn_cast_or_null<CXXMethodDecl>(AFC->getDecl());
 447   if (!MethodDecl)
 448     return;
 449
 450   // Check if an object became moved-from.
 451   // Object can become moved from after a call to move assignment operator or
 452   // move constructor .
 453   const auto *ConstructorDecl = dyn_cast<CXXConstructorDecl>(MethodDecl);
 454   if (ConstructorDecl && !ConstructorDecl->isMoveConstructor())
 455     return;
 456
 457   if (!ConstructorDecl && !MethodDecl->isMoveAssignmentOperator())
 458     return;
 459
 460   const auto ArgRegion = AFC->getArgSVal(0).getAsRegion();
 461   if (!ArgRegion)
 462     return;
 463
 464   // Skip moving the object to itself.
 465   const auto *CC = dyn_cast_or_null<CXXConstructorCall>(&Call);
 466   if (CC && CC->getCXXThisVal().getAsRegion() == ArgRegion)
 467     return;
 468
 469   if (const auto *IC = dyn_cast<CXXInstanceCall>(AFC))
 470     if (IC->getCXXThisVal().getAsRegion() == ArgRegion)
 471       return;
 472
 473   const MemRegion *BaseRegion = ArgRegion->getBaseRegion();
 474   // Skip temp objects because of their short lifetime.
 475   if (BaseRegion->getAs<CXXTempObjectRegion>() ||
 476       AFC->getArgExpr(0)->isPRValue())
 477     return;
 478   // If it has already been reported do not need to modify the state.
 479
 480   if (State->get<TrackedRegionMap>(ArgRegion))
 481     return;
 482
 483   const CXXRecordDecl *RD = MethodDecl->getParent();
 484   ObjectKind OK = classifyObject(ArgRegion, RD);
 485   if (shouldBeTracked(OK)) {
 486     // Mark object as moved-from.
 487     State = State->set<TrackedRegionMap>(ArgRegion, RegionState::getMoved());
 488     C.addTransition(State);
 489     return;
 490   }
 491   assert(!C.isDifferent() && "Should not have made transitions on this path!");
 492 }
 493
 494 bool MoveChecker::isMoveSafeMethod(const CXXMethodDecl *MethodDec) const {
 495   // We abandon the cases where bool/void/void* conversion happens.
 496   if (const auto *ConversionDec =
 497           dyn_cast_or_null<CXXConversionDecl>(MethodDec)) {
 498     const Type *Tp = ConversionDec->getConversionType().getTypePtrOrNull();
 499     if (!Tp)
 500       return false;
 501     if (Tp->isBooleanType() || Tp->isVoidType() || Tp->isVoidPointerType())
 502       return true;
 503   }
 504   // Function call `empty` can be skipped.
 505   return (MethodDec && MethodDec->getDeclName().isIdentifier() &&
 506       (MethodDec->getName().lower() == "empty" ||
 507        MethodDec->getName().lower() == "isempty"));
 508 }
 509
 510 bool MoveChecker::isStateResetMethod(const CXXMethodDecl *MethodDec) const {
 511   if (!MethodDec)
 512       return false;
 513   if (MethodDec->hasAttr<ReinitializesAttr>())
 514       return true;
 515   if (MethodDec->getDeclName().isIdentifier()) {
 516     std::string MethodName = MethodDec->getName().lower();
 517     // TODO: Some of these methods (eg., resize) are not always resetting
 518     // the state, so we should consider looking at the arguments.
 519     if (MethodName == "assign" || MethodName == "clear" ||
 520         MethodName == "destroy" || MethodName == "reset" ||
 521         MethodName == "resize" || MethodName == "shrink")
 522       return true;
 523   }
 524   return false;
 525 }
 526
 527 // Don't report an error inside a move related operation.
 528 // We assume that the programmer knows what she does.
 529 bool MoveChecker::isInMoveSafeContext(const LocationContext *LC) const {
 530   do {
 531     const auto *CtxDec = LC->getDecl();
 532     auto *CtorDec = dyn_cast_or_null<CXXConstructorDecl>(CtxDec);
 533     auto *DtorDec = dyn_cast_or_null<CXXDestructorDecl>(CtxDec);
 534     auto *MethodDec = dyn_cast_or_null<CXXMethodDecl>(CtxDec);
 535     if (DtorDec || (CtorDec && CtorDec->isCopyOrMoveConstructor()) ||
 536         (MethodDec && MethodDec->isOverloadedOperator() &&
 537          MethodDec->getOverloadedOperator() == OO_Equal) ||
 538         isStateResetMethod(MethodDec) || isMoveSafeMethod(MethodDec))
 539       return true;
 540   } while ((LC = LC->getParent()));
 541   return false;
 542 }
 543
 544 bool MoveChecker::belongsTo(const CXXRecordDecl *RD,
 545                             const llvm::StringSet<> &Set) const {
 546   const IdentifierInfo *II = RD->getIdentifier();
 547   return II && Set.count(II->getName());
 548 }
 549
 550 MoveChecker::ObjectKind
 551 MoveChecker::classifyObject(const MemRegion *MR,
 552                             const CXXRecordDecl *RD) const {
 553   // Local variables and local rvalue references are classified as "Local".
 554   // For the purposes of this checker, we classify move-safe STL types
 555   // as not-"STL" types, because that's how the checker treats them.
 556   MR = unwrapRValueReferenceIndirection(MR);
 557   bool IsLocal =
 558       isa_and_nonnull<VarRegion, CXXLifetimeExtendedObjectRegion>(MR) &&
 559       isa<StackSpaceRegion>(MR->getMemorySpace());
 560
 561   if (!RD || !RD->getDeclContext()->isStdNamespace())
 562     return { IsLocal, SK_NonStd };
 563
 564   if (belongsTo(RD, StdSmartPtrClasses))
 565     return { IsLocal, SK_SmartPtr };
 566
 567   if (belongsTo(RD, StdSafeClasses))
 568     return { IsLocal, SK_Safe };
 569
 570   return { IsLocal, SK_Unsafe };
 571 }
 572
 573 void MoveChecker::explainObject(llvm::raw_ostream &OS, const MemRegion *MR,
 574                                 const CXXRecordDecl *RD, MisuseKind MK) const {
 575   // We may need a leading space every time we actually explain anything,
 576   // and we never know if we are to explain anything until we try.
 577   if (const auto DR =
 578           dyn_cast_or_null<DeclRegion>(unwrapRValueReferenceIndirection(MR))) {
 579     const auto *RegionDecl = cast<NamedDecl>(DR->getDecl());
 580     OS << " '" << RegionDecl->getDeclName() << "'";
 581   }
 582
 583   ObjectKind OK = classifyObject(MR, RD);
 584   switch (OK.StdKind) {
 585     case SK_NonStd:
 586     case SK_Safe:
 587       break;
 588     case SK_SmartPtr:
 589       if (MK != MK_Dereference)
 590         break;
 591
 592       // We only care about the type if it's a dereference.
 593       [[fallthrough]];
 594     case SK_Unsafe:
 595       OS << " of type '" << RD->getQualifiedNameAsString() << "'";
 596       break;
 597   };
 598 }
 599
 600 void MoveChecker::checkPreCall(const CallEvent &Call, CheckerContext &C) const {
 601   ProgramStateRef State = C.getState();
 602
 603   // Remove the MemRegions from the map on which a ctor/dtor call or assignment
 604   // happened.
 605
 606   // Checking constructor calls.
 607   if (const auto *CC = dyn_cast<CXXConstructorCall>(&Call)) {
 608     State = removeFromState(State, CC->getCXXThisVal().getAsRegion());
 609     auto CtorDec = CC->getDecl();
 610     // Check for copying a moved-from object and report the bug.
 611     if (CtorDec && CtorDec->isCopyOrMoveConstructor()) {
 612       const MemRegion *ArgRegion = CC->getArgSVal(0).getAsRegion();
 613       const CXXRecordDecl *RD = CtorDec->getParent();
 614       MisuseKind MK = CtorDec->isMoveConstructor() ? MK_Move : MK_Copy;
 615       modelUse(State, ArgRegion, RD, MK, C);
 616       return;
 617     }
 618   }
 619
 620   const auto IC = dyn_cast<CXXInstanceCall>(&Call);
 621   if (!IC)
 622     return;
 623
 624   const MemRegion *ThisRegion = IC->getCXXThisVal().getAsRegion();
 625   if (!ThisRegion)
 626     return;
 627
 628   // The remaining part is check only for method call on a moved-from object.
 629   const auto MethodDecl = dyn_cast_or_null<CXXMethodDecl>(IC->getDecl());
 630   if (!MethodDecl)
 631     return;
 632
 633   // Calling a destructor on a moved object is fine.
 634   if (isa<CXXDestructorDecl>(MethodDecl))
 635     return;
 636
 637   // We want to investigate the whole object, not only sub-object of a parent
 638   // class in which the encountered method defined.
 639   ThisRegion = ThisRegion->getMostDerivedObjectRegion();
 640
 641   if (isStateResetMethod(MethodDecl)) {
 642     State = removeFromState(State, ThisRegion);
 643     C.addTransition(State);
 644     return;
 645   }
 646
 647   if (isMoveSafeMethod(MethodDecl))
 648     return;
 649
 650   // Store class declaration as well, for bug reporting purposes.
 651   const CXXRecordDecl *RD = MethodDecl->getParent();
 652
 653   if (MethodDecl->isOverloadedOperator()) {
 654     OverloadedOperatorKind OOK = MethodDecl->getOverloadedOperator();
 655
 656     if (OOK == OO_Equal) {
 657       // Remove the tracked object for every assignment operator, but report bug
 658       // only for move or copy assignment's argument.
 659       State = removeFromState(State, ThisRegion);
 660
 661       if (MethodDecl->isCopyAssignmentOperator() ||
 662           MethodDecl->isMoveAssignmentOperator()) {
 663         const MemRegion *ArgRegion = IC->getArgSVal(0).getAsRegion();
 664         MisuseKind MK =
 665             MethodDecl->isMoveAssignmentOperator() ? MK_Move : MK_Copy;
 666         modelUse(State, ArgRegion, RD, MK, C);
 667         return;
 668       }
 669       C.addTransition(State);
 670       return;
 671     }
 672
 673     if (OOK == OO_Star || OOK == OO_Arrow) {
 674       modelUse(State, ThisRegion, RD, MK_Dereference, C);
 675       return;
 676     }
 677   }
 678
 679   modelUse(State, ThisRegion, RD, MK_FunCall, C);
 680 }
 681
 682 void MoveChecker::checkDeadSymbols(SymbolReaper &SymReaper,
 683                                    CheckerContext &C) const {
 684   ProgramStateRef State = C.getState();
 685   TrackedRegionMapTy TrackedRegions = State->get<TrackedRegionMap>();
 686   for (auto E : TrackedRegions) {
 687     const MemRegion *Region = E.first;
 688     bool IsRegDead = !SymReaper.isLiveRegion(Region);
 689
 690     // Remove the dead regions from the region map.
 691     if (IsRegDead) {
 692       State = State->remove<TrackedRegionMap>(Region);
 693     }
 694   }
 695   C.addTransition(State);
 696 }
 697
 698 ProgramStateRef MoveChecker::checkRegionChanges(
 699     ProgramStateRef State, const InvalidatedSymbols *Invalidated,
 700     ArrayRef<const MemRegion *> RequestedRegions,
 701     ArrayRef<const MemRegion *> InvalidatedRegions,
 702     const LocationContext *LCtx, const CallEvent *Call) const {
 703   if (Call) {
 704     // Relax invalidation upon function calls: only invalidate parameters
 705     // that are passed directly via non-const pointers or non-const references
 706     // or rvalue references.
 707     // In case of an InstanceCall don't invalidate the this-region since
 708     // it is fully handled in checkPreCall and checkPostCall.
 709     const MemRegion *ThisRegion = nullptr;
 710     if (const auto *IC = dyn_cast<CXXInstanceCall>(Call))
 711       ThisRegion = IC->getCXXThisVal().getAsRegion();
 712
 713     // Requested ("explicit") regions are the regions passed into the call
 714     // directly, but not all of them end up being invalidated.
 715     // But when they do, they appear in the InvalidatedRegions array as well.
 716     for (const auto *Region : RequestedRegions) {
 717       if (ThisRegion != Region &&
 718           llvm::is_contained(InvalidatedRegions, Region))
 719         State = removeFromState(State, Region);
 720     }
 721   } else {
 722     // For invalidations that aren't caused by calls, assume nothing. In
 723     // particular, direct write into an object's field invalidates the status.
 724     for (const auto *Region : InvalidatedRegions)
 725       State = removeFromState(State, Region->getBaseRegion());
 726   }
 727
 728   return State;
 729 }
 730
 731 void MoveChecker::printState(raw_ostream &Out, ProgramStateRef State,
 732                              const char *NL, const char *Sep) const {
 733
 734   TrackedRegionMapTy RS = State->get<TrackedRegionMap>();
 735
 736   if (!RS.isEmpty()) {
 737     Out << Sep << "Moved-from objects :" << NL;
 738     for (auto I: RS) {
 739       I.first->dumpToStream(Out);
 740       if (I.second.isMoved())
 741         Out << ": moved";
 742       else
 743         Out << ": moved and reported";
 744       Out << NL;
 745     }
 746   }
 747 }
 748 void ento::registerMoveChecker(CheckerManager &mgr) {
 749   MoveChecker *chk = mgr.registerChecker<MoveChecker>();
 750   chk->setAggressiveness(
 751       mgr.getAnalyzerOptions().getCheckerStringOption(chk, "WarnOn"), mgr);
 752 }
 753
 754 bool ento::shouldRegisterMoveChecker(const CheckerManager &mgr) {
 755   return true;
 756 }