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      1 //== SymbolManager.h - Management of Symbolic 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 defines SymbolManager, a class that manages symbolic values
     11 //  created for use by ExprEngine and related classes.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #ifndef LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_SYMBOLMANAGER_H
     16 #define LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_SYMBOLMANAGER_H
     17 
     18 #include "clang/AST/Decl.h"
     19 #include "clang/AST/Expr.h"
     20 #include "clang/Analysis/AnalysisContext.h"
     21 #include "clang/Basic/LLVM.h"
     22 #include "clang/StaticAnalyzer/Core/PathSensitive/StoreRef.h"
     23 #include "llvm/ADT/DenseMap.h"
     24 #include "llvm/ADT/DenseSet.h"
     25 #include "llvm/ADT/FoldingSet.h"
     26 #include "llvm/Support/Allocator.h"
     27 #include "llvm/Support/DataTypes.h"
     28 
     29 namespace clang {
     30   class ASTContext;
     31   class StackFrameContext;
     32 
     33 namespace ento {
     34   class BasicValueFactory;
     35   class MemRegion;
     36   class SubRegion;
     37   class TypedValueRegion;
     38   class VarRegion;
     39 
     40 /// \brief Symbolic value. These values used to capture symbolic execution of
     41 /// the program.
     42 class SymExpr : public llvm::FoldingSetNode {
     43   virtual void anchor();
     44 public:
     45   enum Kind { RegionValueKind, ConjuredKind, DerivedKind, ExtentKind,
     46               MetadataKind,
     47               BEGIN_SYMBOLS = RegionValueKind,
     48               END_SYMBOLS = MetadataKind,
     49               SymIntKind, IntSymKind, SymSymKind,
     50               BEGIN_BINARYSYMEXPRS = SymIntKind,
     51               END_BINARYSYMEXPRS = SymSymKind,
     52               CastSymbolKind };
     53 private:
     54   Kind K;
     55 
     56 protected:
     57   SymExpr(Kind k) : K(k) {}
     58 
     59 public:
     60   virtual ~SymExpr() {}
     61 
     62   Kind getKind() const { return K; }
     63 
     64   virtual void dump() const;
     65 
     66   virtual void dumpToStream(raw_ostream &os) const {}
     67 
     68   virtual QualType getType() const = 0;
     69   virtual void Profile(llvm::FoldingSetNodeID& profile) = 0;
     70 
     71   /// \brief Iterator over symbols that the current symbol depends on.
     72   ///
     73   /// For SymbolData, it's the symbol itself; for expressions, it's the
     74   /// expression symbol and all the operands in it. Note, SymbolDerived is
     75   /// treated as SymbolData - the iterator will NOT visit the parent region.
     76   class symbol_iterator {
     77     SmallVector<const SymExpr*, 5> itr;
     78     void expand();
     79   public:
     80     symbol_iterator() {}
     81     symbol_iterator(const SymExpr *SE);
     82 
     83     symbol_iterator &operator++();
     84     const SymExpr* operator*();
     85 
     86     bool operator==(const symbol_iterator &X) const;
     87     bool operator!=(const symbol_iterator &X) const;
     88   };
     89 
     90   symbol_iterator symbol_begin() const {
     91     return symbol_iterator(this);
     92   }
     93   static symbol_iterator symbol_end() { return symbol_iterator(); }
     94 
     95   unsigned computeComplexity() const;
     96 };
     97 
     98 typedef const SymExpr* SymbolRef;
     99 typedef SmallVector<SymbolRef, 2> SymbolRefSmallVectorTy;
    100 
    101 typedef unsigned SymbolID;
    102 /// \brief A symbol representing data which can be stored in a memory location
    103 /// (region).
    104 class SymbolData : public SymExpr {
    105   void anchor() override;
    106   const SymbolID Sym;
    107 
    108 protected:
    109   SymbolData(Kind k, SymbolID sym) : SymExpr(k), Sym(sym) {}
    110 
    111 public:
    112   ~SymbolData() override {}
    113 
    114   SymbolID getSymbolID() const { return Sym; }
    115 
    116   // Implement isa<T> support.
    117   static inline bool classof(const SymExpr *SE) {
    118     Kind k = SE->getKind();
    119     return k >= BEGIN_SYMBOLS && k <= END_SYMBOLS;
    120   }
    121 };
    122 
    123 ///\brief A symbol representing the value stored at a MemRegion.
    124 class SymbolRegionValue : public SymbolData {
    125   const TypedValueRegion *R;
    126 
    127 public:
    128   SymbolRegionValue(SymbolID sym, const TypedValueRegion *r)
    129     : SymbolData(RegionValueKind, sym), R(r) {}
    130 
    131   const TypedValueRegion* getRegion() const { return R; }
    132 
    133   static void Profile(llvm::FoldingSetNodeID& profile, const TypedValueRegion* R) {
    134     profile.AddInteger((unsigned) RegionValueKind);
    135     profile.AddPointer(R);
    136   }
    137 
    138   void Profile(llvm::FoldingSetNodeID& profile) override {
    139     Profile(profile, R);
    140   }
    141 
    142   void dumpToStream(raw_ostream &os) const override;
    143 
    144   QualType getType() const override;
    145 
    146   // Implement isa<T> support.
    147   static inline bool classof(const SymExpr *SE) {
    148     return SE->getKind() == RegionValueKind;
    149   }
    150 };
    151 
    152 /// A symbol representing the result of an expression in the case when we do
    153 /// not know anything about what the expression is.
    154 class SymbolConjured : public SymbolData {
    155   const Stmt *S;
    156   QualType T;
    157   unsigned Count;
    158   const LocationContext *LCtx;
    159   const void *SymbolTag;
    160 
    161 public:
    162   SymbolConjured(SymbolID sym, const Stmt *s, const LocationContext *lctx,
    163 		 QualType t, unsigned count,
    164                  const void *symbolTag)
    165     : SymbolData(ConjuredKind, sym), S(s), T(t), Count(count),
    166       LCtx(lctx),
    167       SymbolTag(symbolTag) {}
    168 
    169   const Stmt *getStmt() const { return S; }
    170   unsigned getCount() const { return Count; }
    171   const void *getTag() const { return SymbolTag; }
    172 
    173   QualType getType() const override;
    174 
    175   void dumpToStream(raw_ostream &os) const override;
    176 
    177   static void Profile(llvm::FoldingSetNodeID& profile, const Stmt *S,
    178                       QualType T, unsigned Count, const LocationContext *LCtx,
    179                       const void *SymbolTag) {
    180     profile.AddInteger((unsigned) ConjuredKind);
    181     profile.AddPointer(S);
    182     profile.AddPointer(LCtx);
    183     profile.Add(T);
    184     profile.AddInteger(Count);
    185     profile.AddPointer(SymbolTag);
    186   }
    187 
    188   void Profile(llvm::FoldingSetNodeID& profile) override {
    189     Profile(profile, S, T, Count, LCtx, SymbolTag);
    190   }
    191 
    192   // Implement isa<T> support.
    193   static inline bool classof(const SymExpr *SE) {
    194     return SE->getKind() == ConjuredKind;
    195   }
    196 };
    197 
    198 /// A symbol representing the value of a MemRegion whose parent region has
    199 /// symbolic value.
    200 class SymbolDerived : public SymbolData {
    201   SymbolRef parentSymbol;
    202   const TypedValueRegion *R;
    203 
    204 public:
    205   SymbolDerived(SymbolID sym, SymbolRef parent, const TypedValueRegion *r)
    206     : SymbolData(DerivedKind, sym), parentSymbol(parent), R(r) {}
    207 
    208   SymbolRef getParentSymbol() const { return parentSymbol; }
    209   const TypedValueRegion *getRegion() const { return R; }
    210 
    211   QualType getType() const override;
    212 
    213   void dumpToStream(raw_ostream &os) const override;
    214 
    215   static void Profile(llvm::FoldingSetNodeID& profile, SymbolRef parent,
    216                       const TypedValueRegion *r) {
    217     profile.AddInteger((unsigned) DerivedKind);
    218     profile.AddPointer(r);
    219     profile.AddPointer(parent);
    220   }
    221 
    222   void Profile(llvm::FoldingSetNodeID& profile) override {
    223     Profile(profile, parentSymbol, R);
    224   }
    225 
    226   // Implement isa<T> support.
    227   static inline bool classof(const SymExpr *SE) {
    228     return SE->getKind() == DerivedKind;
    229   }
    230 };
    231 
    232 /// SymbolExtent - Represents the extent (size in bytes) of a bounded region.
    233 ///  Clients should not ask the SymbolManager for a region's extent. Always use
    234 ///  SubRegion::getExtent instead -- the value returned may not be a symbol.
    235 class SymbolExtent : public SymbolData {
    236   const SubRegion *R;
    237 
    238 public:
    239   SymbolExtent(SymbolID sym, const SubRegion *r)
    240   : SymbolData(ExtentKind, sym), R(r) {}
    241 
    242   const SubRegion *getRegion() const { return R; }
    243 
    244   QualType getType() const override;
    245 
    246   void dumpToStream(raw_ostream &os) const override;
    247 
    248   static void Profile(llvm::FoldingSetNodeID& profile, const SubRegion *R) {
    249     profile.AddInteger((unsigned) ExtentKind);
    250     profile.AddPointer(R);
    251   }
    252 
    253   void Profile(llvm::FoldingSetNodeID& profile) override {
    254     Profile(profile, R);
    255   }
    256 
    257   // Implement isa<T> support.
    258   static inline bool classof(const SymExpr *SE) {
    259     return SE->getKind() == ExtentKind;
    260   }
    261 };
    262 
    263 /// SymbolMetadata - Represents path-dependent metadata about a specific region.
    264 ///  Metadata symbols remain live as long as they are marked as in use before
    265 ///  dead-symbol sweeping AND their associated regions are still alive.
    266 ///  Intended for use by checkers.
    267 class SymbolMetadata : public SymbolData {
    268   const MemRegion* R;
    269   const Stmt *S;
    270   QualType T;
    271   unsigned Count;
    272   const void *Tag;
    273 public:
    274   SymbolMetadata(SymbolID sym, const MemRegion* r, const Stmt *s, QualType t,
    275                  unsigned count, const void *tag)
    276   : SymbolData(MetadataKind, sym), R(r), S(s), T(t), Count(count), Tag(tag) {}
    277 
    278   const MemRegion *getRegion() const { return R; }
    279   const Stmt *getStmt() const { return S; }
    280   unsigned getCount() const { return Count; }
    281   const void *getTag() const { return Tag; }
    282 
    283   QualType getType() const override;
    284 
    285   void dumpToStream(raw_ostream &os) const override;
    286 
    287   static void Profile(llvm::FoldingSetNodeID& profile, const MemRegion *R,
    288                       const Stmt *S, QualType T, unsigned Count,
    289                       const void *Tag) {
    290     profile.AddInteger((unsigned) MetadataKind);
    291     profile.AddPointer(R);
    292     profile.AddPointer(S);
    293     profile.Add(T);
    294     profile.AddInteger(Count);
    295     profile.AddPointer(Tag);
    296   }
    297 
    298   void Profile(llvm::FoldingSetNodeID& profile) override {
    299     Profile(profile, R, S, T, Count, Tag);
    300   }
    301 
    302   // Implement isa<T> support.
    303   static inline bool classof(const SymExpr *SE) {
    304     return SE->getKind() == MetadataKind;
    305   }
    306 };
    307 
    308 /// \brief Represents a cast expression.
    309 class SymbolCast : public SymExpr {
    310   const SymExpr *Operand;
    311   /// Type of the operand.
    312   QualType FromTy;
    313   /// The type of the result.
    314   QualType ToTy;
    315 
    316 public:
    317   SymbolCast(const SymExpr *In, QualType From, QualType To) :
    318     SymExpr(CastSymbolKind), Operand(In), FromTy(From), ToTy(To) { }
    319 
    320   QualType getType() const override { return ToTy; }
    321 
    322   const SymExpr *getOperand() const { return Operand; }
    323 
    324   void dumpToStream(raw_ostream &os) const override;
    325 
    326   static void Profile(llvm::FoldingSetNodeID& ID,
    327                       const SymExpr *In, QualType From, QualType To) {
    328     ID.AddInteger((unsigned) CastSymbolKind);
    329     ID.AddPointer(In);
    330     ID.Add(From);
    331     ID.Add(To);
    332   }
    333 
    334   void Profile(llvm::FoldingSetNodeID& ID) override {
    335     Profile(ID, Operand, FromTy, ToTy);
    336   }
    337 
    338   // Implement isa<T> support.
    339   static inline bool classof(const SymExpr *SE) {
    340     return SE->getKind() == CastSymbolKind;
    341   }
    342 };
    343 
    344 /// \brief Represents a symbolic expression involving a binary operator
    345 class BinarySymExpr : public SymExpr {
    346   BinaryOperator::Opcode Op;
    347   QualType T;
    348 
    349 protected:
    350   BinarySymExpr(Kind k, BinaryOperator::Opcode op, QualType t)
    351     : SymExpr(k), Op(op), T(t) {}
    352 
    353 public:
    354   // FIXME: We probably need to make this out-of-line to avoid redundant
    355   // generation of virtual functions.
    356   QualType getType() const override { return T; }
    357 
    358   BinaryOperator::Opcode getOpcode() const { return Op; }
    359 
    360   // Implement isa<T> support.
    361   static inline bool classof(const SymExpr *SE) {
    362     Kind k = SE->getKind();
    363     return k >= BEGIN_BINARYSYMEXPRS && k <= END_BINARYSYMEXPRS;
    364   }
    365 };
    366 
    367 /// \brief Represents a symbolic expression like 'x' + 3.
    368 class SymIntExpr : public BinarySymExpr {
    369   const SymExpr *LHS;
    370   const llvm::APSInt& RHS;
    371 
    372 public:
    373   SymIntExpr(const SymExpr *lhs, BinaryOperator::Opcode op,
    374              const llvm::APSInt& rhs, QualType t)
    375     : BinarySymExpr(SymIntKind, op, t), LHS(lhs), RHS(rhs) {}
    376 
    377   void dumpToStream(raw_ostream &os) const override;
    378 
    379   const SymExpr *getLHS() const { return LHS; }
    380   const llvm::APSInt &getRHS() const { return RHS; }
    381 
    382   static void Profile(llvm::FoldingSetNodeID& ID, const SymExpr *lhs,
    383                       BinaryOperator::Opcode op, const llvm::APSInt& rhs,
    384                       QualType t) {
    385     ID.AddInteger((unsigned) SymIntKind);
    386     ID.AddPointer(lhs);
    387     ID.AddInteger(op);
    388     ID.AddPointer(&rhs);
    389     ID.Add(t);
    390   }
    391 
    392   void Profile(llvm::FoldingSetNodeID& ID) override {
    393     Profile(ID, LHS, getOpcode(), RHS, getType());
    394   }
    395 
    396   // Implement isa<T> support.
    397   static inline bool classof(const SymExpr *SE) {
    398     return SE->getKind() == SymIntKind;
    399   }
    400 };
    401 
    402 /// \brief Represents a symbolic expression like 3 - 'x'.
    403 class IntSymExpr : public BinarySymExpr {
    404   const llvm::APSInt& LHS;
    405   const SymExpr *RHS;
    406 
    407 public:
    408   IntSymExpr(const llvm::APSInt& lhs, BinaryOperator::Opcode op,
    409              const SymExpr *rhs, QualType t)
    410     : BinarySymExpr(IntSymKind, op, t), LHS(lhs), RHS(rhs) {}
    411 
    412   void dumpToStream(raw_ostream &os) const override;
    413 
    414   const SymExpr *getRHS() const { return RHS; }
    415   const llvm::APSInt &getLHS() const { return LHS; }
    416 
    417   static void Profile(llvm::FoldingSetNodeID& ID, const llvm::APSInt& lhs,
    418                       BinaryOperator::Opcode op, const SymExpr *rhs,
    419                       QualType t) {
    420     ID.AddInteger((unsigned) IntSymKind);
    421     ID.AddPointer(&lhs);
    422     ID.AddInteger(op);
    423     ID.AddPointer(rhs);
    424     ID.Add(t);
    425   }
    426 
    427   void Profile(llvm::FoldingSetNodeID& ID) override {
    428     Profile(ID, LHS, getOpcode(), RHS, getType());
    429   }
    430 
    431   // Implement isa<T> support.
    432   static inline bool classof(const SymExpr *SE) {
    433     return SE->getKind() == IntSymKind;
    434   }
    435 };
    436 
    437 /// \brief Represents a symbolic expression like 'x' + 'y'.
    438 class SymSymExpr : public BinarySymExpr {
    439   const SymExpr *LHS;
    440   const SymExpr *RHS;
    441 
    442 public:
    443   SymSymExpr(const SymExpr *lhs, BinaryOperator::Opcode op, const SymExpr *rhs,
    444              QualType t)
    445     : BinarySymExpr(SymSymKind, op, t), LHS(lhs), RHS(rhs) {}
    446 
    447   const SymExpr *getLHS() const { return LHS; }
    448   const SymExpr *getRHS() const { return RHS; }
    449 
    450   void dumpToStream(raw_ostream &os) const override;
    451 
    452   static void Profile(llvm::FoldingSetNodeID& ID, const SymExpr *lhs,
    453                     BinaryOperator::Opcode op, const SymExpr *rhs, QualType t) {
    454     ID.AddInteger((unsigned) SymSymKind);
    455     ID.AddPointer(lhs);
    456     ID.AddInteger(op);
    457     ID.AddPointer(rhs);
    458     ID.Add(t);
    459   }
    460 
    461   void Profile(llvm::FoldingSetNodeID& ID) override {
    462     Profile(ID, LHS, getOpcode(), RHS, getType());
    463   }
    464 
    465   // Implement isa<T> support.
    466   static inline bool classof(const SymExpr *SE) {
    467     return SE->getKind() == SymSymKind;
    468   }
    469 };
    470 
    471 class SymbolManager {
    472   typedef llvm::FoldingSet<SymExpr> DataSetTy;
    473   typedef llvm::DenseMap<SymbolRef, SymbolRefSmallVectorTy*> SymbolDependTy;
    474 
    475   DataSetTy DataSet;
    476   /// Stores the extra dependencies between symbols: the data should be kept
    477   /// alive as long as the key is live.
    478   SymbolDependTy SymbolDependencies;
    479   unsigned SymbolCounter;
    480   llvm::BumpPtrAllocator& BPAlloc;
    481   BasicValueFactory &BV;
    482   ASTContext &Ctx;
    483 
    484 public:
    485   SymbolManager(ASTContext &ctx, BasicValueFactory &bv,
    486                 llvm::BumpPtrAllocator& bpalloc)
    487     : SymbolDependencies(16), SymbolCounter(0),
    488       BPAlloc(bpalloc), BV(bv), Ctx(ctx) {}
    489 
    490   ~SymbolManager();
    491 
    492   static bool canSymbolicate(QualType T);
    493 
    494   /// \brief Make a unique symbol for MemRegion R according to its kind.
    495   const SymbolRegionValue* getRegionValueSymbol(const TypedValueRegion* R);
    496 
    497   const SymbolConjured* conjureSymbol(const Stmt *E,
    498                                       const LocationContext *LCtx,
    499                                       QualType T,
    500                                       unsigned VisitCount,
    501                                       const void *SymbolTag = nullptr);
    502 
    503   const SymbolConjured* conjureSymbol(const Expr *E,
    504                                       const LocationContext *LCtx,
    505                                       unsigned VisitCount,
    506                                       const void *SymbolTag = nullptr) {
    507     return conjureSymbol(E, LCtx, E->getType(), VisitCount, SymbolTag);
    508   }
    509 
    510   const SymbolDerived *getDerivedSymbol(SymbolRef parentSymbol,
    511                                         const TypedValueRegion *R);
    512 
    513   const SymbolExtent *getExtentSymbol(const SubRegion *R);
    514 
    515   /// \brief Creates a metadata symbol associated with a specific region.
    516   ///
    517   /// VisitCount can be used to differentiate regions corresponding to
    518   /// different loop iterations, thus, making the symbol path-dependent.
    519   const SymbolMetadata *getMetadataSymbol(const MemRegion *R, const Stmt *S,
    520                                           QualType T, unsigned VisitCount,
    521                                           const void *SymbolTag = nullptr);
    522 
    523   const SymbolCast* getCastSymbol(const SymExpr *Operand,
    524                                   QualType From, QualType To);
    525 
    526   const SymIntExpr *getSymIntExpr(const SymExpr *lhs, BinaryOperator::Opcode op,
    527                                   const llvm::APSInt& rhs, QualType t);
    528 
    529   const SymIntExpr *getSymIntExpr(const SymExpr &lhs, BinaryOperator::Opcode op,
    530                                   const llvm::APSInt& rhs, QualType t) {
    531     return getSymIntExpr(&lhs, op, rhs, t);
    532   }
    533 
    534   const IntSymExpr *getIntSymExpr(const llvm::APSInt& lhs,
    535                                   BinaryOperator::Opcode op,
    536                                   const SymExpr *rhs, QualType t);
    537 
    538   const SymSymExpr *getSymSymExpr(const SymExpr *lhs, BinaryOperator::Opcode op,
    539                                   const SymExpr *rhs, QualType t);
    540 
    541   QualType getType(const SymExpr *SE) const {
    542     return SE->getType();
    543   }
    544 
    545   /// \brief Add artificial symbol dependency.
    546   ///
    547   /// The dependent symbol should stay alive as long as the primary is alive.
    548   void addSymbolDependency(const SymbolRef Primary, const SymbolRef Dependent);
    549 
    550   const SymbolRefSmallVectorTy *getDependentSymbols(const SymbolRef Primary);
    551 
    552   ASTContext &getContext() { return Ctx; }
    553   BasicValueFactory &getBasicVals() { return BV; }
    554 };
    555 
    556 /// \brief A class responsible for cleaning up unused symbols.
    557 class SymbolReaper {
    558   enum SymbolStatus {
    559     NotProcessed,
    560     HaveMarkedDependents
    561   };
    562 
    563   typedef llvm::DenseSet<SymbolRef> SymbolSetTy;
    564   typedef llvm::DenseMap<SymbolRef, SymbolStatus> SymbolMapTy;
    565   typedef llvm::DenseSet<const MemRegion *> RegionSetTy;
    566 
    567   SymbolMapTy TheLiving;
    568   SymbolSetTy MetadataInUse;
    569   SymbolSetTy TheDead;
    570 
    571   RegionSetTy RegionRoots;
    572 
    573   const StackFrameContext *LCtx;
    574   const Stmt *Loc;
    575   SymbolManager& SymMgr;
    576   StoreRef reapedStore;
    577   llvm::DenseMap<const MemRegion *, unsigned> includedRegionCache;
    578 
    579 public:
    580   /// \brief Construct a reaper object, which removes everything which is not
    581   /// live before we execute statement s in the given location context.
    582   ///
    583   /// If the statement is NULL, everything is this and parent contexts is
    584   /// considered live.
    585   /// If the stack frame context is NULL, everything on stack is considered
    586   /// dead.
    587   SymbolReaper(const StackFrameContext *Ctx, const Stmt *s, SymbolManager& symmgr,
    588                StoreManager &storeMgr)
    589    : LCtx(Ctx), Loc(s), SymMgr(symmgr),
    590      reapedStore(nullptr, storeMgr) {}
    591 
    592   const LocationContext *getLocationContext() const { return LCtx; }
    593 
    594   bool isLive(SymbolRef sym);
    595   bool isLiveRegion(const MemRegion *region);
    596   bool isLive(const Stmt *ExprVal, const LocationContext *LCtx) const;
    597   bool isLive(const VarRegion *VR, bool includeStoreBindings = false) const;
    598 
    599   /// \brief Unconditionally marks a symbol as live.
    600   ///
    601   /// This should never be
    602   /// used by checkers, only by the state infrastructure such as the store and
    603   /// environment. Checkers should instead use metadata symbols and markInUse.
    604   void markLive(SymbolRef sym);
    605 
    606   /// \brief Marks a symbol as important to a checker.
    607   ///
    608   /// For metadata symbols,
    609   /// this will keep the symbol alive as long as its associated region is also
    610   /// live. For other symbols, this has no effect; checkers are not permitted
    611   /// to influence the life of other symbols. This should be used before any
    612   /// symbol marking has occurred, i.e. in the MarkLiveSymbols callback.
    613   void markInUse(SymbolRef sym);
    614 
    615   /// \brief If a symbol is known to be live, marks the symbol as live.
    616   ///
    617   ///  Otherwise, if the symbol cannot be proven live, it is marked as dead.
    618   ///  Returns true if the symbol is dead, false if live.
    619   bool maybeDead(SymbolRef sym);
    620 
    621   typedef SymbolSetTy::const_iterator dead_iterator;
    622   dead_iterator dead_begin() const { return TheDead.begin(); }
    623   dead_iterator dead_end() const { return TheDead.end(); }
    624 
    625   bool hasDeadSymbols() const {
    626     return !TheDead.empty();
    627   }
    628 
    629   typedef RegionSetTy::const_iterator region_iterator;
    630   region_iterator region_begin() const { return RegionRoots.begin(); }
    631   region_iterator region_end() const { return RegionRoots.end(); }
    632 
    633   /// \brief Returns whether or not a symbol has been confirmed dead.
    634   ///
    635   /// This should only be called once all marking of dead symbols has completed.
    636   /// (For checkers, this means only in the evalDeadSymbols callback.)
    637   bool isDead(SymbolRef sym) const {
    638     return TheDead.count(sym);
    639   }
    640 
    641   void markLive(const MemRegion *region);
    642   void markElementIndicesLive(const MemRegion *region);
    643 
    644   /// \brief Set to the value of the symbolic store after
    645   /// StoreManager::removeDeadBindings has been called.
    646   void setReapedStore(StoreRef st) { reapedStore = st; }
    647 
    648 private:
    649   /// Mark the symbols dependent on the input symbol as live.
    650   void markDependentsLive(SymbolRef sym);
    651 };
    652 
    653 class SymbolVisitor {
    654 protected:
    655   ~SymbolVisitor() = default;
    656 
    657 public:
    658   SymbolVisitor() = default;
    659   SymbolVisitor(const SymbolVisitor &) = default;
    660   SymbolVisitor(SymbolVisitor &&) {}
    661 
    662   /// \brief A visitor method invoked by ProgramStateManager::scanReachableSymbols.
    663   ///
    664   /// The method returns \c true if symbols should continue be scanned and \c
    665   /// false otherwise.
    666   virtual bool VisitSymbol(SymbolRef sym) = 0;
    667   virtual bool VisitMemRegion(const MemRegion *region) { return true; }
    668 };
    669 
    670 } // end GR namespace
    671 
    672 } // end clang namespace
    673 
    674 namespace llvm {
    675 static inline raw_ostream &operator<<(raw_ostream &os,
    676                                       const clang::ento::SymExpr *SE) {
    677   SE->dumpToStream(os);
    678   return os;
    679 }
    680 } // end llvm namespace
    681 #endif
    682