1 //===- ConstraintManager.h - Constraints on symbolic values. ----*- C++ -*-===//
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
9 // This file defined the interface to manage constraints on symbolic values.
11 //===----------------------------------------------------------------------===//
13 #ifndef LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CONSTRAINTMANAGER_H
14 #define LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CONSTRAINTMANAGER_H
16 #include "clang/Basic/LLVM.h"
17 #include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState_Fwd.h"
18 #include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
19 #include "clang/StaticAnalyzer/Core/PathSensitive/SymExpr.h"
20 #include "llvm/ADT/Optional.h"
21 #include "llvm/Support/SaveAndRestore.h"
34 class ProgramStateManager;
38 class ConditionTruthVal {
42 /// Construct a ConditionTruthVal indicating the constraint is constrained
43 /// to either true or false, depending on the boolean value provided.
44 ConditionTruthVal(bool constraint) : Val(constraint) {}
46 /// Construct a ConstraintVal indicating the constraint is underconstrained.
47 ConditionTruthVal() = default;
49 /// \return Stored value, assuming that the value is known.
50 /// Crashes otherwise.
51 bool getValue() const {
55 /// Return true if the constraint is perfectly constrained to 'true'.
56 bool isConstrainedTrue() const {
57 return Val.hasValue() && Val.getValue();
60 /// Return true if the constraint is perfectly constrained to 'false'.
61 bool isConstrainedFalse() const {
62 return Val.hasValue() && !Val.getValue();
65 /// Return true if the constrained is perfectly constrained.
66 bool isConstrained() const {
67 return Val.hasValue();
70 /// Return true if the constrained is underconstrained and we do not know
71 /// if the constraint is true of value.
72 bool isUnderconstrained() const {
73 return !Val.hasValue();
77 class ConstraintManager {
79 ConstraintManager() = default;
80 virtual ~ConstraintManager();
82 virtual bool haveEqualConstraints(ProgramStateRef S1,
83 ProgramStateRef S2) const = 0;
85 virtual ProgramStateRef assume(ProgramStateRef state,
89 using ProgramStatePair = std::pair<ProgramStateRef, ProgramStateRef>;
91 /// Returns a pair of states (StTrue, StFalse) where the given condition is
92 /// assumed to be true or false, respectively.
93 ProgramStatePair assumeDual(ProgramStateRef State, DefinedSVal Cond) {
94 ProgramStateRef StTrue = assume(State, Cond, true);
96 // If StTrue is infeasible, asserting the falseness of Cond is unnecessary
97 // because the existing constraints already establish this.
100 // This check is expensive and should be disabled even in Release+Asserts
102 // FIXME: __OPTIMIZE__ is a GNU extension that Clang implements but MSVC
103 // does not. Is there a good equivalent there?
104 assert(assume(State, Cond, false) && "System is over constrained.");
106 return ProgramStatePair((ProgramStateRef)nullptr, State);
109 ProgramStateRef StFalse = assume(State, Cond, false);
111 // We are careful to return the original state, /not/ StTrue,
112 // because we want to avoid having callers generate a new node
113 // in the ExplodedGraph.
114 return ProgramStatePair(State, (ProgramStateRef)nullptr);
117 return ProgramStatePair(StTrue, StFalse);
120 virtual ProgramStateRef assumeInclusiveRange(ProgramStateRef State,
122 const llvm::APSInt &From,
123 const llvm::APSInt &To,
126 virtual ProgramStatePair assumeInclusiveRangeDual(ProgramStateRef State,
128 const llvm::APSInt &From,
129 const llvm::APSInt &To) {
130 ProgramStateRef StInRange =
131 assumeInclusiveRange(State, Value, From, To, true);
133 // If StTrue is infeasible, asserting the falseness of Cond is unnecessary
134 // because the existing constraints already establish this.
136 return ProgramStatePair((ProgramStateRef)nullptr, State);
138 ProgramStateRef StOutOfRange =
139 assumeInclusiveRange(State, Value, From, To, false);
141 // We are careful to return the original state, /not/ StTrue,
142 // because we want to avoid having callers generate a new node
143 // in the ExplodedGraph.
144 return ProgramStatePair(State, (ProgramStateRef)nullptr);
147 return ProgramStatePair(StInRange, StOutOfRange);
150 /// If a symbol is perfectly constrained to a constant, attempt
151 /// to return the concrete value.
153 /// Note that a ConstraintManager is not obligated to return a concretized
154 /// value for a symbol, even if it is perfectly constrained.
155 virtual const llvm::APSInt* getSymVal(ProgramStateRef state,
156 SymbolRef sym) const {
160 /// Scan all symbols referenced by the constraints. If the symbol is not
161 /// alive, remove it.
162 virtual ProgramStateRef removeDeadBindings(ProgramStateRef state,
163 SymbolReaper& SymReaper) = 0;
165 virtual void printJson(raw_ostream &Out, ProgramStateRef State,
166 const char *NL, unsigned int Space,
167 bool IsDot) const = 0;
169 /// Convenience method to query the state to see if a symbol is null or
170 /// not null, or if neither assumption can be made.
171 ConditionTruthVal isNull(ProgramStateRef State, SymbolRef Sym) {
172 SaveAndRestore<bool> DisableNotify(NotifyAssumeClients, false);
174 return checkNull(State, Sym);
178 /// A flag to indicate that clients should be notified of assumptions.
179 /// By default this is the case, but sometimes this needs to be restricted
180 /// to avoid infinite recursions within the ConstraintManager.
182 /// Note that this flag allows the ConstraintManager to be re-entrant,
183 /// but not thread-safe.
184 bool NotifyAssumeClients = true;
186 /// canReasonAbout - Not all ConstraintManagers can accurately reason about
187 /// all SVal values. This method returns true if the ConstraintManager can
188 /// reasonably handle a given SVal value. This is typically queried by
189 /// ExprEngine to determine if the value should be replaced with a
190 /// conjured symbolic value in order to recover some precision.
191 virtual bool canReasonAbout(SVal X) const = 0;
193 /// Returns whether or not a symbol is known to be null ("true"), known to be
194 /// non-null ("false"), or may be either ("underconstrained").
195 virtual ConditionTruthVal checkNull(ProgramStateRef State, SymbolRef Sym);
198 std::unique_ptr<ConstraintManager>
199 CreateRangeConstraintManager(ProgramStateManager &statemgr,
200 SubEngine *subengine);
202 std::unique_ptr<ConstraintManager>
203 CreateZ3ConstraintManager(ProgramStateManager &statemgr, SubEngine *subengine);
208 #endif // LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CONSTRAINTMANAGER_H