clang  3.7.0
ConstraintManager.h
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1 //== ConstraintManager.h - Constraints on 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 defined the interface to manage constraints on symbolic values.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CONSTRAINTMANAGER_H
15 #define LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CONSTRAINTMANAGER_H
16 
19 #include "llvm/Support/SaveAndRestore.h"
20 
21 namespace llvm {
22 class APSInt;
23 }
24 
25 namespace clang {
26 namespace ento {
27 
28 class SubEngine;
29 
31  Optional<bool> Val;
32 public:
33  /// Construct a ConditionTruthVal indicating the constraint is constrained
34  /// to either true or false, depending on the boolean value provided.
35  ConditionTruthVal(bool constraint) : Val(constraint) {}
36 
37  /// Construct a ConstraintVal indicating the constraint is underconstrained.
39 
40  /// Return true if the constraint is perfectly constrained to 'true'.
41  bool isConstrainedTrue() const {
42  return Val.hasValue() && Val.getValue();
43  }
44 
45  /// Return true if the constraint is perfectly constrained to 'false'.
46  bool isConstrainedFalse() const {
47  return Val.hasValue() && !Val.getValue();
48  }
49 
50  /// Return true if the constrained is perfectly constrained.
51  bool isConstrained() const {
52  return Val.hasValue();
53  }
54 
55  /// Return true if the constrained is underconstrained and we do not know
56  /// if the constraint is true of value.
57  bool isUnderconstrained() const {
58  return !Val.hasValue();
59  }
60 };
61 
63 public:
65 
66  virtual ~ConstraintManager();
68  DefinedSVal Cond,
69  bool Assumption) = 0;
70 
71  typedef std::pair<ProgramStateRef, ProgramStateRef> ProgramStatePair;
72 
73  /// Returns a pair of states (StTrue, StFalse) where the given condition is
74  /// assumed to be true or false, respectively.
76  ProgramStateRef StTrue = assume(State, Cond, true);
77 
78  // If StTrue is infeasible, asserting the falseness of Cond is unnecessary
79  // because the existing constraints already establish this.
80  if (!StTrue) {
81 #ifndef __OPTIMIZE__
82  // This check is expensive and should be disabled even in Release+Asserts
83  // builds.
84  // FIXME: __OPTIMIZE__ is a GNU extension that Clang implements but MSVC
85  // does not. Is there a good equivalent there?
86  assert(assume(State, Cond, false) && "System is over constrained.");
87 #endif
88  return ProgramStatePair((ProgramStateRef)nullptr, State);
89  }
90 
91  ProgramStateRef StFalse = assume(State, Cond, false);
92  if (!StFalse) {
93  // We are careful to return the original state, /not/ StTrue,
94  // because we want to avoid having callers generate a new node
95  // in the ExplodedGraph.
96  return ProgramStatePair(State, (ProgramStateRef)nullptr);
97  }
98 
99  return ProgramStatePair(StTrue, StFalse);
100  }
101 
102  /// \brief If a symbol is perfectly constrained to a constant, attempt
103  /// to return the concrete value.
104  ///
105  /// Note that a ConstraintManager is not obligated to return a concretized
106  /// value for a symbol, even if it is perfectly constrained.
107  virtual const llvm::APSInt* getSymVal(ProgramStateRef state,
108  SymbolRef sym) const {
109  return nullptr;
110  }
111 
113  SymbolReaper& SymReaper) = 0;
114 
115  virtual void print(ProgramStateRef state,
116  raw_ostream &Out,
117  const char* nl,
118  const char *sep) = 0;
119 
120  virtual void EndPath(ProgramStateRef state) {}
121 
122  /// Convenience method to query the state to see if a symbol is null or
123  /// not null, or if neither assumption can be made.
125  SaveAndRestore<bool> DisableNotify(NotifyAssumeClients, false);
126 
127  return checkNull(State, Sym);
128  }
129 
130 protected:
131  /// A flag to indicate that clients should be notified of assumptions.
132  /// By default this is the case, but sometimes this needs to be restricted
133  /// to avoid infinite recursions within the ConstraintManager.
134  ///
135  /// Note that this flag allows the ConstraintManager to be re-entrant,
136  /// but not thread-safe.
138 
139  /// canReasonAbout - Not all ConstraintManagers can accurately reason about
140  /// all SVal values. This method returns true if the ConstraintManager can
141  /// reasonably handle a given SVal value. This is typically queried by
142  /// ExprEngine to determine if the value should be replaced with a
143  /// conjured symbolic value in order to recover some precision.
144  virtual bool canReasonAbout(SVal X) const = 0;
145 
146  /// Returns whether or not a symbol is known to be null ("true"), known to be
147  /// non-null ("false"), or may be either ("underconstrained").
149 };
150 
151 std::unique_ptr<ConstraintManager>
153  SubEngine *subengine);
154 
155 } // end GR namespace
156 
157 } // end clang namespace
158 
159 #endif
virtual ProgramStateRef assume(ProgramStateRef state, DefinedSVal Cond, bool Assumption)=0
bool isConstrainedFalse() const
Return true if the constraint is perfectly constrained to 'false'.
std::unique_ptr< ConstraintManager > CreateRangeConstraintManager(ProgramStateManager &statemgr, SubEngine *subengine)
virtual void EndPath(ProgramStateRef state)
virtual ConditionTruthVal checkNull(ProgramStateRef State, SymbolRef Sym)
Symbolic value. These values used to capture symbolic execution of the program.
Definition: SymbolManager.h:42
ConditionTruthVal isNull(ProgramStateRef State, SymbolRef Sym)
LineState State
virtual void print(ProgramStateRef state, raw_ostream &Out, const char *nl, const char *sep)=0
ProgramStatePair assumeDual(ProgramStateRef State, DefinedSVal Cond)
virtual ProgramStateRef removeDeadBindings(ProgramStateRef state, SymbolReaper &SymReaper)=0
std::pair< ProgramStateRef, ProgramStateRef > ProgramStatePair
A class responsible for cleaning up unused symbols.
virtual bool canReasonAbout(SVal X) const =0
bool isConstrainedTrue() const
Return true if the constraint is perfectly constrained to 'true'.
ConditionTruthVal()
Construct a ConstraintVal indicating the constraint is underconstrained.
X
Definition: SemaDecl.cpp:11429
bool isConstrained() const
Return true if the constrained is perfectly constrained.
virtual const llvm::APSInt * getSymVal(ProgramStateRef state, SymbolRef sym) const
If a symbol is perfectly constrained to a constant, attempt to return the concrete value...
#define true
Definition: stdbool.h:32