1 //===- SymExpr.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 SymExpr and SymbolData.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_SYMEXPR_H
15 #define LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_SYMEXPR_H
16 
17 #include "clang/AST/Type.h"
18 #include "clang/Basic/LLVM.h"
19 #include "llvm/ADT/FoldingSet.h"
20 #include "llvm/ADT/SmallVector.h"
21 #include <cassert>
22 
23 namespace clang {
24 namespace ento {
25 
26 class MemRegion;
27 
28 /// Symbolic value. These values used to capture symbolic execution of
29 /// the program.
30 class SymExpr : public llvm::FoldingSetNode {
31   virtual void anchor();
32 
33 public:
34   enum Kind {
35 #define SYMBOL(Id, Parent) Id##Kind,
36 #define SYMBOL_RANGE(Id, First, Last) BEGIN_##Id = First, END_##Id = Last,
37 #include "clang/StaticAnalyzer/Core/PathSensitive/Symbols.def"
38   };
39 
40 private:
41   Kind K;
42 
43 protected:
SymExpr(Kind k)44   SymExpr(Kind k) : K(k) {}
45 
isValidTypeForSymbol(QualType T)46   static bool isValidTypeForSymbol(QualType T) {
47     // FIXME: Depending on whether we choose to deprecate structural symbols,
48     // this may become much stricter.
49     return !T.isNull() && !T->isVoidType();
50   }
51 
52   mutable unsigned Complexity = 0;
53 
54 public:
55   virtual ~SymExpr() = default;
56 
getKind()57   Kind getKind() const { return K; }
58 
59   virtual void dump() const;
60 
dumpToStream(raw_ostream & os)61   virtual void dumpToStream(raw_ostream &os) const {}
62 
63   virtual QualType getType() const = 0;
64   virtual void Profile(llvm::FoldingSetNodeID &profile) = 0;
65 
66   /// Iterator over symbols that the current symbol depends on.
67   ///
68   /// For SymbolData, it's the symbol itself; for expressions, it's the
69   /// expression symbol and all the operands in it. Note, SymbolDerived is
70   /// treated as SymbolData - the iterator will NOT visit the parent region.
71   class symbol_iterator {
72     SmallVector<const SymExpr *, 5> itr;
73 
74     void expand();
75 
76   public:
77     symbol_iterator() = default;
78     symbol_iterator(const SymExpr *SE);
79 
80     symbol_iterator &operator++();
81     const SymExpr *operator*();
82 
83     bool operator==(const symbol_iterator &X) const;
84     bool operator!=(const symbol_iterator &X) const;
85   };
86 
symbol_begin()87   symbol_iterator symbol_begin() const { return symbol_iterator(this); }
symbol_end()88   static symbol_iterator symbol_end() { return symbol_iterator(); }
89 
90   virtual unsigned computeComplexity() const = 0;
91 
92   /// Find the region from which this symbol originates.
93   ///
94   /// Whenever the symbol was constructed to denote an unknown value of
95   /// a certain memory region, return this region. This method
96   /// allows checkers to make decisions depending on the origin of the symbol.
97   /// Symbol classes for which the origin region is known include
98   /// SymbolRegionValue which denotes the value of the region before
99   /// the beginning of the analysis, and SymbolDerived which denotes the value
100   /// of a certain memory region after its super region (a memory space or
101   /// a larger record region) is default-bound with a certain symbol.
getOriginRegion()102   virtual const MemRegion *getOriginRegion() const { return nullptr; }
103 };
104 
105 inline raw_ostream &operator<<(raw_ostream &os,
106                                const clang::ento::SymExpr *SE) {
107   SE->dumpToStream(os);
108   return os;
109 }
110 
111 using SymbolRef = const SymExpr *;
112 using SymbolRefSmallVectorTy = SmallVector<SymbolRef, 2>;
113 using SymbolID = unsigned;
114 
115 /// A symbol representing data which can be stored in a memory location
116 /// (region).
117 class SymbolData : public SymExpr {
118   const SymbolID Sym;
119 
120   void anchor() override;
121 
122 protected:
SymbolData(Kind k,SymbolID sym)123   SymbolData(Kind k, SymbolID sym) : SymExpr(k), Sym(sym) {
124     assert(classof(this));
125   }
126 
127 public:
128   ~SymbolData() override = default;
129 
getSymbolID()130   SymbolID getSymbolID() const { return Sym; }
131 
computeComplexity()132   unsigned computeComplexity() const override {
133     return 1;
134   };
135 
136   // Implement isa<T> support.
classof(const SymExpr * SE)137   static inline bool classof(const SymExpr *SE) {
138     Kind k = SE->getKind();
139     return k >= BEGIN_SYMBOLS && k <= END_SYMBOLS;
140   }
141 };
142 
143 } // namespace ento
144 } // namespace clang
145 
146 #endif // LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_SYMEXPR_H
147