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_GR_CONSTRAINT_MANAGER_H
15#define LLVM_CLANG_GR_CONSTRAINT_MANAGER_H
16
17#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
18#include "clang/StaticAnalyzer/Core/PathSensitive/SymbolManager.h"
19#include "llvm/Support/SaveAndRestore.h"
20
21namespace llvm {
22class APSInt;
23}
24
25namespace clang {
26namespace ento {
27
28class SubEngine;
29
30class ConditionTruthVal {
31  Optional<bool> Val;
32public:
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.
38  ConditionTruthVal() {}
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
62class ConstraintManager {
63public:
64  ConstraintManager() : NotifyAssumeClients(true) {}
65
66  virtual ~ConstraintManager();
67  virtual ProgramStateRef assume(ProgramStateRef state,
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.
75  ProgramStatePair assumeDual(ProgramStateRef State, DefinedSVal Cond) {
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
112  virtual ProgramStateRef removeDeadBindings(ProgramStateRef state,
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.
124  ConditionTruthVal isNull(ProgramStateRef State, SymbolRef Sym) {
125    SaveAndRestore<bool> DisableNotify(NotifyAssumeClients, false);
126
127    return checkNull(State, Sym);
128  }
129
130protected:
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.
137  bool NotifyAssumeClients;
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").
148  virtual ConditionTruthVal checkNull(ProgramStateRef State, SymbolRef Sym);
149};
150
151ConstraintManager* CreateRangeConstraintManager(ProgramStateManager& statemgr,
152                                                SubEngine *subengine);
153
154} // end GR namespace
155
156} // end clang namespace
157
158#endif
159