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      1 //= ProgramState.cpp - Path-Sensitive "State" for tracking values --*- C++ -*--=
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 //  This file implements ProgramState and ProgramStateManager.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
     15 #include "clang/Analysis/CFG.h"
     16 #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
     17 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramStateTrait.h"
     18 #include "clang/StaticAnalyzer/Core/PathSensitive/SubEngine.h"
     19 #include "clang/StaticAnalyzer/Core/PathSensitive/TaintManager.h"
     20 #include "llvm/Support/raw_ostream.h"
     21 
     22 using namespace clang;
     23 using namespace ento;
     24 
     25 namespace clang { namespace  ento {
     26 /// Increments the number of times this state is referenced.
     27 
     28 void ProgramStateRetain(const ProgramState *state) {
     29   ++const_cast<ProgramState*>(state)->refCount;
     30 }
     31 
     32 /// Decrement the number of times this state is referenced.
     33 void ProgramStateRelease(const ProgramState *state) {
     34   assert(state->refCount > 0);
     35   ProgramState *s = const_cast<ProgramState*>(state);
     36   if (--s->refCount == 0) {
     37     ProgramStateManager &Mgr = s->getStateManager();
     38     Mgr.StateSet.RemoveNode(s);
     39     s->~ProgramState();
     40     Mgr.freeStates.push_back(s);
     41   }
     42 }
     43 }}
     44 
     45 ProgramState::ProgramState(ProgramStateManager *mgr, const Environment& env,
     46                  StoreRef st, GenericDataMap gdm)
     47   : stateMgr(mgr),
     48     Env(env),
     49     store(st.getStore()),
     50     GDM(gdm),
     51     refCount(0) {
     52   stateMgr->getStoreManager().incrementReferenceCount(store);
     53 }
     54 
     55 ProgramState::ProgramState(const ProgramState &RHS)
     56     : llvm::FoldingSetNode(),
     57       stateMgr(RHS.stateMgr),
     58       Env(RHS.Env),
     59       store(RHS.store),
     60       GDM(RHS.GDM),
     61       refCount(0) {
     62   stateMgr->getStoreManager().incrementReferenceCount(store);
     63 }
     64 
     65 ProgramState::~ProgramState() {
     66   if (store)
     67     stateMgr->getStoreManager().decrementReferenceCount(store);
     68 }
     69 
     70 ProgramStateManager::ProgramStateManager(ASTContext &Ctx,
     71                                          StoreManagerCreator CreateSMgr,
     72                                          ConstraintManagerCreator CreateCMgr,
     73                                          llvm::BumpPtrAllocator &alloc,
     74                                          SubEngine *SubEng)
     75   : Eng(SubEng), EnvMgr(alloc), GDMFactory(alloc),
     76     svalBuilder(createSimpleSValBuilder(alloc, Ctx, *this)),
     77     CallEventMgr(new CallEventManager(alloc)), Alloc(alloc) {
     78   StoreMgr = (*CreateSMgr)(*this);
     79   ConstraintMgr = (*CreateCMgr)(*this, SubEng);
     80 }
     81 
     82 
     83 ProgramStateManager::~ProgramStateManager() {
     84   for (GDMContextsTy::iterator I=GDMContexts.begin(), E=GDMContexts.end();
     85        I!=E; ++I)
     86     I->second.second(I->second.first);
     87 }
     88 
     89 ProgramStateRef
     90 ProgramStateManager::removeDeadBindings(ProgramStateRef state,
     91                                    const StackFrameContext *LCtx,
     92                                    SymbolReaper& SymReaper) {
     93 
     94   // This code essentially performs a "mark-and-sweep" of the VariableBindings.
     95   // The roots are any Block-level exprs and Decls that our liveness algorithm
     96   // tells us are live.  We then see what Decls they may reference, and keep
     97   // those around.  This code more than likely can be made faster, and the
     98   // frequency of which this method is called should be experimented with
     99   // for optimum performance.
    100   ProgramState NewState = *state;
    101 
    102   NewState.Env = EnvMgr.removeDeadBindings(NewState.Env, SymReaper, state);
    103 
    104   // Clean up the store.
    105   StoreRef newStore = StoreMgr->removeDeadBindings(NewState.getStore(), LCtx,
    106                                                    SymReaper);
    107   NewState.setStore(newStore);
    108   SymReaper.setReapedStore(newStore);
    109 
    110   ProgramStateRef Result = getPersistentState(NewState);
    111   return ConstraintMgr->removeDeadBindings(Result, SymReaper);
    112 }
    113 
    114 ProgramStateRef ProgramState::bindLoc(Loc LV, SVal V, bool notifyChanges) const {
    115   ProgramStateManager &Mgr = getStateManager();
    116   ProgramStateRef newState = makeWithStore(Mgr.StoreMgr->Bind(getStore(),
    117                                                              LV, V));
    118   const MemRegion *MR = LV.getAsRegion();
    119   if (MR && Mgr.getOwningEngine() && notifyChanges)
    120     return Mgr.getOwningEngine()->processRegionChange(newState, MR);
    121 
    122   return newState;
    123 }
    124 
    125 ProgramStateRef ProgramState::bindDefault(SVal loc, SVal V) const {
    126   ProgramStateManager &Mgr = getStateManager();
    127   const MemRegion *R = loc.castAs<loc::MemRegionVal>().getRegion();
    128   const StoreRef &newStore = Mgr.StoreMgr->BindDefault(getStore(), R, V);
    129   ProgramStateRef new_state = makeWithStore(newStore);
    130   return Mgr.getOwningEngine() ?
    131            Mgr.getOwningEngine()->processRegionChange(new_state, R) :
    132            new_state;
    133 }
    134 
    135 typedef ArrayRef<const MemRegion *> RegionList;
    136 typedef ArrayRef<SVal> ValueList;
    137 
    138 ProgramStateRef
    139 ProgramState::invalidateRegions(RegionList Regions,
    140                              const Expr *E, unsigned Count,
    141                              const LocationContext *LCtx,
    142                              bool CausedByPointerEscape,
    143                              InvalidatedSymbols *IS,
    144                              const CallEvent *Call,
    145                              RegionAndSymbolInvalidationTraits *ITraits) const {
    146   SmallVector<SVal, 8> Values;
    147   for (RegionList::const_iterator I = Regions.begin(),
    148                                   End = Regions.end(); I != End; ++I)
    149     Values.push_back(loc::MemRegionVal(*I));
    150 
    151   return invalidateRegionsImpl(Values, E, Count, LCtx, CausedByPointerEscape,
    152                                IS, ITraits, Call);
    153 }
    154 
    155 ProgramStateRef
    156 ProgramState::invalidateRegions(ValueList Values,
    157                              const Expr *E, unsigned Count,
    158                              const LocationContext *LCtx,
    159                              bool CausedByPointerEscape,
    160                              InvalidatedSymbols *IS,
    161                              const CallEvent *Call,
    162                              RegionAndSymbolInvalidationTraits *ITraits) const {
    163 
    164   return invalidateRegionsImpl(Values, E, Count, LCtx, CausedByPointerEscape,
    165                                IS, ITraits, Call);
    166 }
    167 
    168 ProgramStateRef
    169 ProgramState::invalidateRegionsImpl(ValueList Values,
    170                                     const Expr *E, unsigned Count,
    171                                     const LocationContext *LCtx,
    172                                     bool CausedByPointerEscape,
    173                                     InvalidatedSymbols *IS,
    174                                     RegionAndSymbolInvalidationTraits *ITraits,
    175                                     const CallEvent *Call) const {
    176   ProgramStateManager &Mgr = getStateManager();
    177   SubEngine* Eng = Mgr.getOwningEngine();
    178 
    179   InvalidatedSymbols Invalidated;
    180   if (!IS)
    181     IS = &Invalidated;
    182 
    183   RegionAndSymbolInvalidationTraits ITraitsLocal;
    184   if (!ITraits)
    185     ITraits = &ITraitsLocal;
    186 
    187   if (Eng) {
    188     StoreManager::InvalidatedRegions TopLevelInvalidated;
    189     StoreManager::InvalidatedRegions Invalidated;
    190     const StoreRef &newStore
    191     = Mgr.StoreMgr->invalidateRegions(getStore(), Values, E, Count, LCtx, Call,
    192                                       *IS, *ITraits, &TopLevelInvalidated,
    193                                       &Invalidated);
    194 
    195     ProgramStateRef newState = makeWithStore(newStore);
    196 
    197     if (CausedByPointerEscape) {
    198       newState = Eng->notifyCheckersOfPointerEscape(newState, IS,
    199                                                     TopLevelInvalidated,
    200                                                     Invalidated, Call,
    201                                                     *ITraits);
    202     }
    203 
    204     return Eng->processRegionChanges(newState, IS, TopLevelInvalidated,
    205                                      Invalidated, Call);
    206   }
    207 
    208   const StoreRef &newStore =
    209   Mgr.StoreMgr->invalidateRegions(getStore(), Values, E, Count, LCtx, Call,
    210                                   *IS, *ITraits, nullptr, nullptr);
    211   return makeWithStore(newStore);
    212 }
    213 
    214 ProgramStateRef ProgramState::killBinding(Loc LV) const {
    215   assert(!LV.getAs<loc::MemRegionVal>() && "Use invalidateRegion instead.");
    216 
    217   Store OldStore = getStore();
    218   const StoreRef &newStore =
    219     getStateManager().StoreMgr->killBinding(OldStore, LV);
    220 
    221   if (newStore.getStore() == OldStore)
    222     return this;
    223 
    224   return makeWithStore(newStore);
    225 }
    226 
    227 ProgramStateRef
    228 ProgramState::enterStackFrame(const CallEvent &Call,
    229                               const StackFrameContext *CalleeCtx) const {
    230   const StoreRef &NewStore =
    231     getStateManager().StoreMgr->enterStackFrame(getStore(), Call, CalleeCtx);
    232   return makeWithStore(NewStore);
    233 }
    234 
    235 SVal ProgramState::getSValAsScalarOrLoc(const MemRegion *R) const {
    236   // We only want to do fetches from regions that we can actually bind
    237   // values.  For example, SymbolicRegions of type 'id<...>' cannot
    238   // have direct bindings (but their can be bindings on their subregions).
    239   if (!R->isBoundable())
    240     return UnknownVal();
    241 
    242   if (const TypedValueRegion *TR = dyn_cast<TypedValueRegion>(R)) {
    243     QualType T = TR->getValueType();
    244     if (Loc::isLocType(T) || T->isIntegralOrEnumerationType())
    245       return getSVal(R);
    246   }
    247 
    248   return UnknownVal();
    249 }
    250 
    251 SVal ProgramState::getSVal(Loc location, QualType T) const {
    252   SVal V = getRawSVal(cast<Loc>(location), T);
    253 
    254   // If 'V' is a symbolic value that is *perfectly* constrained to
    255   // be a constant value, use that value instead to lessen the burden
    256   // on later analysis stages (so we have less symbolic values to reason
    257   // about).
    258   if (!T.isNull()) {
    259     if (SymbolRef sym = V.getAsSymbol()) {
    260       if (const llvm::APSInt *Int = getStateManager()
    261                                     .getConstraintManager()
    262                                     .getSymVal(this, sym)) {
    263         // FIXME: Because we don't correctly model (yet) sign-extension
    264         // and truncation of symbolic values, we need to convert
    265         // the integer value to the correct signedness and bitwidth.
    266         //
    267         // This shows up in the following:
    268         //
    269         //   char foo();
    270         //   unsigned x = foo();
    271         //   if (x == 54)
    272         //     ...
    273         //
    274         //  The symbolic value stored to 'x' is actually the conjured
    275         //  symbol for the call to foo(); the type of that symbol is 'char',
    276         //  not unsigned.
    277         const llvm::APSInt &NewV = getBasicVals().Convert(T, *Int);
    278 
    279         if (V.getAs<Loc>())
    280           return loc::ConcreteInt(NewV);
    281         else
    282           return nonloc::ConcreteInt(NewV);
    283       }
    284     }
    285   }
    286 
    287   return V;
    288 }
    289 
    290 ProgramStateRef ProgramState::BindExpr(const Stmt *S,
    291                                            const LocationContext *LCtx,
    292                                            SVal V, bool Invalidate) const{
    293   Environment NewEnv =
    294     getStateManager().EnvMgr.bindExpr(Env, EnvironmentEntry(S, LCtx), V,
    295                                       Invalidate);
    296   if (NewEnv == Env)
    297     return this;
    298 
    299   ProgramState NewSt = *this;
    300   NewSt.Env = NewEnv;
    301   return getStateManager().getPersistentState(NewSt);
    302 }
    303 
    304 ProgramStateRef ProgramState::assumeInBound(DefinedOrUnknownSVal Idx,
    305                                       DefinedOrUnknownSVal UpperBound,
    306                                       bool Assumption,
    307                                       QualType indexTy) const {
    308   if (Idx.isUnknown() || UpperBound.isUnknown())
    309     return this;
    310 
    311   // Build an expression for 0 <= Idx < UpperBound.
    312   // This is the same as Idx + MIN < UpperBound + MIN, if overflow is allowed.
    313   // FIXME: This should probably be part of SValBuilder.
    314   ProgramStateManager &SM = getStateManager();
    315   SValBuilder &svalBuilder = SM.getSValBuilder();
    316   ASTContext &Ctx = svalBuilder.getContext();
    317 
    318   // Get the offset: the minimum value of the array index type.
    319   BasicValueFactory &BVF = svalBuilder.getBasicValueFactory();
    320   // FIXME: This should be using ValueManager::ArrayindexTy...somehow.
    321   if (indexTy.isNull())
    322     indexTy = Ctx.IntTy;
    323   nonloc::ConcreteInt Min(BVF.getMinValue(indexTy));
    324 
    325   // Adjust the index.
    326   SVal newIdx = svalBuilder.evalBinOpNN(this, BO_Add,
    327                                         Idx.castAs<NonLoc>(), Min, indexTy);
    328   if (newIdx.isUnknownOrUndef())
    329     return this;
    330 
    331   // Adjust the upper bound.
    332   SVal newBound =
    333     svalBuilder.evalBinOpNN(this, BO_Add, UpperBound.castAs<NonLoc>(),
    334                             Min, indexTy);
    335 
    336   if (newBound.isUnknownOrUndef())
    337     return this;
    338 
    339   // Build the actual comparison.
    340   SVal inBound = svalBuilder.evalBinOpNN(this, BO_LT, newIdx.castAs<NonLoc>(),
    341                                          newBound.castAs<NonLoc>(), Ctx.IntTy);
    342   if (inBound.isUnknownOrUndef())
    343     return this;
    344 
    345   // Finally, let the constraint manager take care of it.
    346   ConstraintManager &CM = SM.getConstraintManager();
    347   return CM.assume(this, inBound.castAs<DefinedSVal>(), Assumption);
    348 }
    349 
    350 ConditionTruthVal ProgramState::isNull(SVal V) const {
    351   if (V.isZeroConstant())
    352     return true;
    353 
    354   if (V.isConstant())
    355     return false;
    356 
    357   SymbolRef Sym = V.getAsSymbol(/* IncludeBaseRegion */ true);
    358   if (!Sym)
    359     return ConditionTruthVal();
    360 
    361   return getStateManager().ConstraintMgr->isNull(this, Sym);
    362 }
    363 
    364 ProgramStateRef ProgramStateManager::getInitialState(const LocationContext *InitLoc) {
    365   ProgramState State(this,
    366                 EnvMgr.getInitialEnvironment(),
    367                 StoreMgr->getInitialStore(InitLoc),
    368                 GDMFactory.getEmptyMap());
    369 
    370   return getPersistentState(State);
    371 }
    372 
    373 ProgramStateRef ProgramStateManager::getPersistentStateWithGDM(
    374                                                      ProgramStateRef FromState,
    375                                                      ProgramStateRef GDMState) {
    376   ProgramState NewState(*FromState);
    377   NewState.GDM = GDMState->GDM;
    378   return getPersistentState(NewState);
    379 }
    380 
    381 ProgramStateRef ProgramStateManager::getPersistentState(ProgramState &State) {
    382 
    383   llvm::FoldingSetNodeID ID;
    384   State.Profile(ID);
    385   void *InsertPos;
    386 
    387   if (ProgramState *I = StateSet.FindNodeOrInsertPos(ID, InsertPos))
    388     return I;
    389 
    390   ProgramState *newState = nullptr;
    391   if (!freeStates.empty()) {
    392     newState = freeStates.back();
    393     freeStates.pop_back();
    394   }
    395   else {
    396     newState = (ProgramState*) Alloc.Allocate<ProgramState>();
    397   }
    398   new (newState) ProgramState(State);
    399   StateSet.InsertNode(newState, InsertPos);
    400   return newState;
    401 }
    402 
    403 ProgramStateRef ProgramState::makeWithStore(const StoreRef &store) const {
    404   ProgramState NewSt(*this);
    405   NewSt.setStore(store);
    406   return getStateManager().getPersistentState(NewSt);
    407 }
    408 
    409 void ProgramState::setStore(const StoreRef &newStore) {
    410   Store newStoreStore = newStore.getStore();
    411   if (newStoreStore)
    412     stateMgr->getStoreManager().incrementReferenceCount(newStoreStore);
    413   if (store)
    414     stateMgr->getStoreManager().decrementReferenceCount(store);
    415   store = newStoreStore;
    416 }
    417 
    418 //===----------------------------------------------------------------------===//
    419 //  State pretty-printing.
    420 //===----------------------------------------------------------------------===//
    421 
    422 void ProgramState::print(raw_ostream &Out,
    423                          const char *NL, const char *Sep) const {
    424   // Print the store.
    425   ProgramStateManager &Mgr = getStateManager();
    426   Mgr.getStoreManager().print(getStore(), Out, NL, Sep);
    427 
    428   // Print out the environment.
    429   Env.print(Out, NL, Sep);
    430 
    431   // Print out the constraints.
    432   Mgr.getConstraintManager().print(this, Out, NL, Sep);
    433 
    434   // Print checker-specific data.
    435   Mgr.getOwningEngine()->printState(Out, this, NL, Sep);
    436 }
    437 
    438 void ProgramState::printDOT(raw_ostream &Out) const {
    439   print(Out, "\\l", "\\|");
    440 }
    441 
    442 void ProgramState::dump() const {
    443   print(llvm::errs());
    444 }
    445 
    446 void ProgramState::printTaint(raw_ostream &Out,
    447                               const char *NL, const char *Sep) const {
    448   TaintMapImpl TM = get<TaintMap>();
    449 
    450   if (!TM.isEmpty())
    451     Out <<"Tainted Symbols:" << NL;
    452 
    453   for (TaintMapImpl::iterator I = TM.begin(), E = TM.end(); I != E; ++I) {
    454     Out << I->first << " : " << I->second << NL;
    455   }
    456 }
    457 
    458 void ProgramState::dumpTaint() const {
    459   printTaint(llvm::errs());
    460 }
    461 
    462 //===----------------------------------------------------------------------===//
    463 // Generic Data Map.
    464 //===----------------------------------------------------------------------===//
    465 
    466 void *const* ProgramState::FindGDM(void *K) const {
    467   return GDM.lookup(K);
    468 }
    469 
    470 void*
    471 ProgramStateManager::FindGDMContext(void *K,
    472                                void *(*CreateContext)(llvm::BumpPtrAllocator&),
    473                                void (*DeleteContext)(void*)) {
    474 
    475   std::pair<void*, void (*)(void*)>& p = GDMContexts[K];
    476   if (!p.first) {
    477     p.first = CreateContext(Alloc);
    478     p.second = DeleteContext;
    479   }
    480 
    481   return p.first;
    482 }
    483 
    484 ProgramStateRef ProgramStateManager::addGDM(ProgramStateRef St, void *Key, void *Data){
    485   ProgramState::GenericDataMap M1 = St->getGDM();
    486   ProgramState::GenericDataMap M2 = GDMFactory.add(M1, Key, Data);
    487 
    488   if (M1 == M2)
    489     return St;
    490 
    491   ProgramState NewSt = *St;
    492   NewSt.GDM = M2;
    493   return getPersistentState(NewSt);
    494 }
    495 
    496 ProgramStateRef ProgramStateManager::removeGDM(ProgramStateRef state, void *Key) {
    497   ProgramState::GenericDataMap OldM = state->getGDM();
    498   ProgramState::GenericDataMap NewM = GDMFactory.remove(OldM, Key);
    499 
    500   if (NewM == OldM)
    501     return state;
    502 
    503   ProgramState NewState = *state;
    504   NewState.GDM = NewM;
    505   return getPersistentState(NewState);
    506 }
    507 
    508 bool ScanReachableSymbols::scan(nonloc::LazyCompoundVal val) {
    509   bool wasVisited = !visited.insert(val.getCVData()).second;
    510   if (wasVisited)
    511     return true;
    512 
    513   StoreManager &StoreMgr = state->getStateManager().getStoreManager();
    514   // FIXME: We don't really want to use getBaseRegion() here because pointer
    515   // arithmetic doesn't apply, but scanReachableSymbols only accepts base
    516   // regions right now.
    517   const MemRegion *R = val.getRegion()->getBaseRegion();
    518   return StoreMgr.scanReachableSymbols(val.getStore(), R, *this);
    519 }
    520 
    521 bool ScanReachableSymbols::scan(nonloc::CompoundVal val) {
    522   for (nonloc::CompoundVal::iterator I=val.begin(), E=val.end(); I!=E; ++I)
    523     if (!scan(*I))
    524       return false;
    525 
    526   return true;
    527 }
    528 
    529 bool ScanReachableSymbols::scan(const SymExpr *sym) {
    530   bool wasVisited = !visited.insert(sym).second;
    531   if (wasVisited)
    532     return true;
    533 
    534   if (!visitor.VisitSymbol(sym))
    535     return false;
    536 
    537   // TODO: should be rewritten using SymExpr::symbol_iterator.
    538   switch (sym->getKind()) {
    539     case SymExpr::RegionValueKind:
    540     case SymExpr::ConjuredKind:
    541     case SymExpr::DerivedKind:
    542     case SymExpr::ExtentKind:
    543     case SymExpr::MetadataKind:
    544       break;
    545     case SymExpr::CastSymbolKind:
    546       return scan(cast<SymbolCast>(sym)->getOperand());
    547     case SymExpr::SymIntKind:
    548       return scan(cast<SymIntExpr>(sym)->getLHS());
    549     case SymExpr::IntSymKind:
    550       return scan(cast<IntSymExpr>(sym)->getRHS());
    551     case SymExpr::SymSymKind: {
    552       const SymSymExpr *x = cast<SymSymExpr>(sym);
    553       return scan(x->getLHS()) && scan(x->getRHS());
    554     }
    555   }
    556   return true;
    557 }
    558 
    559 bool ScanReachableSymbols::scan(SVal val) {
    560   if (Optional<loc::MemRegionVal> X = val.getAs<loc::MemRegionVal>())
    561     return scan(X->getRegion());
    562 
    563   if (Optional<nonloc::LazyCompoundVal> X =
    564           val.getAs<nonloc::LazyCompoundVal>())
    565     return scan(*X);
    566 
    567   if (Optional<nonloc::LocAsInteger> X = val.getAs<nonloc::LocAsInteger>())
    568     return scan(X->getLoc());
    569 
    570   if (SymbolRef Sym = val.getAsSymbol())
    571     return scan(Sym);
    572 
    573   if (const SymExpr *Sym = val.getAsSymbolicExpression())
    574     return scan(Sym);
    575 
    576   if (Optional<nonloc::CompoundVal> X = val.getAs<nonloc::CompoundVal>())
    577     return scan(*X);
    578 
    579   return true;
    580 }
    581 
    582 bool ScanReachableSymbols::scan(const MemRegion *R) {
    583   if (isa<MemSpaceRegion>(R))
    584     return true;
    585 
    586   bool wasVisited = !visited.insert(R).second;
    587   if (wasVisited)
    588     return true;
    589 
    590   if (!visitor.VisitMemRegion(R))
    591     return false;
    592 
    593   // If this is a symbolic region, visit the symbol for the region.
    594   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(R))
    595     if (!visitor.VisitSymbol(SR->getSymbol()))
    596       return false;
    597 
    598   // If this is a subregion, also visit the parent regions.
    599   if (const SubRegion *SR = dyn_cast<SubRegion>(R)) {
    600     const MemRegion *Super = SR->getSuperRegion();
    601     if (!scan(Super))
    602       return false;
    603 
    604     // When we reach the topmost region, scan all symbols in it.
    605     if (isa<MemSpaceRegion>(Super)) {
    606       StoreManager &StoreMgr = state->getStateManager().getStoreManager();
    607       if (!StoreMgr.scanReachableSymbols(state->getStore(), SR, *this))
    608         return false;
    609     }
    610   }
    611 
    612   // Regions captured by a block are also implicitly reachable.
    613   if (const BlockDataRegion *BDR = dyn_cast<BlockDataRegion>(R)) {
    614     BlockDataRegion::referenced_vars_iterator I = BDR->referenced_vars_begin(),
    615                                               E = BDR->referenced_vars_end();
    616     for ( ; I != E; ++I) {
    617       if (!scan(I.getCapturedRegion()))
    618         return false;
    619     }
    620   }
    621 
    622   return true;
    623 }
    624 
    625 bool ProgramState::scanReachableSymbols(SVal val, SymbolVisitor& visitor) const {
    626   ScanReachableSymbols S(this, visitor);
    627   return S.scan(val);
    628 }
    629 
    630 bool ProgramState::scanReachableSymbols(const SVal *I, const SVal *E,
    631                                    SymbolVisitor &visitor) const {
    632   ScanReachableSymbols S(this, visitor);
    633   for ( ; I != E; ++I) {
    634     if (!S.scan(*I))
    635       return false;
    636   }
    637   return true;
    638 }
    639 
    640 bool ProgramState::scanReachableSymbols(const MemRegion * const *I,
    641                                    const MemRegion * const *E,
    642                                    SymbolVisitor &visitor) const {
    643   ScanReachableSymbols S(this, visitor);
    644   for ( ; I != E; ++I) {
    645     if (!S.scan(*I))
    646       return false;
    647   }
    648   return true;
    649 }
    650 
    651 ProgramStateRef ProgramState::addTaint(const Stmt *S,
    652                                            const LocationContext *LCtx,
    653                                            TaintTagType Kind) const {
    654   if (const Expr *E = dyn_cast_or_null<Expr>(S))
    655     S = E->IgnoreParens();
    656 
    657   SymbolRef Sym = getSVal(S, LCtx).getAsSymbol();
    658   if (Sym)
    659     return addTaint(Sym, Kind);
    660 
    661   const MemRegion *R = getSVal(S, LCtx).getAsRegion();
    662   addTaint(R, Kind);
    663 
    664   // Cannot add taint, so just return the state.
    665   return this;
    666 }
    667 
    668 ProgramStateRef ProgramState::addTaint(const MemRegion *R,
    669                                            TaintTagType Kind) const {
    670   if (const SymbolicRegion *SR = dyn_cast_or_null<SymbolicRegion>(R))
    671     return addTaint(SR->getSymbol(), Kind);
    672   return this;
    673 }
    674 
    675 ProgramStateRef ProgramState::addTaint(SymbolRef Sym,
    676                                            TaintTagType Kind) const {
    677   // If this is a symbol cast, remove the cast before adding the taint. Taint
    678   // is cast agnostic.
    679   while (const SymbolCast *SC = dyn_cast<SymbolCast>(Sym))
    680     Sym = SC->getOperand();
    681 
    682   ProgramStateRef NewState = set<TaintMap>(Sym, Kind);
    683   assert(NewState);
    684   return NewState;
    685 }
    686 
    687 bool ProgramState::isTainted(const Stmt *S, const LocationContext *LCtx,
    688                              TaintTagType Kind) const {
    689   if (const Expr *E = dyn_cast_or_null<Expr>(S))
    690     S = E->IgnoreParens();
    691 
    692   SVal val = getSVal(S, LCtx);
    693   return isTainted(val, Kind);
    694 }
    695 
    696 bool ProgramState::isTainted(SVal V, TaintTagType Kind) const {
    697   if (const SymExpr *Sym = V.getAsSymExpr())
    698     return isTainted(Sym, Kind);
    699   if (const MemRegion *Reg = V.getAsRegion())
    700     return isTainted(Reg, Kind);
    701   return false;
    702 }
    703 
    704 bool ProgramState::isTainted(const MemRegion *Reg, TaintTagType K) const {
    705   if (!Reg)
    706     return false;
    707 
    708   // Element region (array element) is tainted if either the base or the offset
    709   // are tainted.
    710   if (const ElementRegion *ER = dyn_cast<ElementRegion>(Reg))
    711     return isTainted(ER->getSuperRegion(), K) || isTainted(ER->getIndex(), K);
    712 
    713   if (const SymbolicRegion *SR = dyn_cast<SymbolicRegion>(Reg))
    714     return isTainted(SR->getSymbol(), K);
    715 
    716   if (const SubRegion *ER = dyn_cast<SubRegion>(Reg))
    717     return isTainted(ER->getSuperRegion(), K);
    718 
    719   return false;
    720 }
    721 
    722 bool ProgramState::isTainted(SymbolRef Sym, TaintTagType Kind) const {
    723   if (!Sym)
    724     return false;
    725 
    726   // Traverse all the symbols this symbol depends on to see if any are tainted.
    727   bool Tainted = false;
    728   for (SymExpr::symbol_iterator SI = Sym->symbol_begin(), SE =Sym->symbol_end();
    729        SI != SE; ++SI) {
    730     if (!isa<SymbolData>(*SI))
    731       continue;
    732 
    733     const TaintTagType *Tag = get<TaintMap>(*SI);
    734     Tainted = (Tag && *Tag == Kind);
    735 
    736     // If this is a SymbolDerived with a tainted parent, it's also tainted.
    737     if (const SymbolDerived *SD = dyn_cast<SymbolDerived>(*SI))
    738       Tainted = Tainted || isTainted(SD->getParentSymbol(), Kind);
    739 
    740     // If memory region is tainted, data is also tainted.
    741     if (const SymbolRegionValue *SRV = dyn_cast<SymbolRegionValue>(*SI))
    742       Tainted = Tainted || isTainted(SRV->getRegion(), Kind);
    743 
    744     // If If this is a SymbolCast from a tainted value, it's also tainted.
    745     if (const SymbolCast *SC = dyn_cast<SymbolCast>(*SI))
    746       Tainted = Tainted || isTainted(SC->getOperand(), Kind);
    747 
    748     if (Tainted)
    749       return true;
    750   }
    751 
    752   return Tainted;
    753 }
    754 
    755