//===- ConstraintManager.h - Constraints on symbolic values. ----*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

//  This file defined the interface to manage constraints on symbolic values.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CONSTRAINTMANAGER_H

#define LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CONSTRAINTMANAGER_H

#include "clang/Basic/LLVM.h"

#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState_Fwd.h"

#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"

#include "clang/StaticAnalyzer/Core/PathSensitive/SymExpr.h"

#include "llvm/ADT/Optional.h"

#include "llvm/Support/SaveAndRestore.h"

#include <memory>

#include <utility>

namespace llvm {

class APSInt;

} // namespace llvm

namespace clang {

namespace ento {

class ProgramStateManager;

class ExprEngine;

class SymbolReaper;

class ConditionTruthVal {

  Optional<bool> Val;

public:

  /// Construct a ConditionTruthVal indicating the constraint is constrained

  /// to either true or false, depending on the boolean value provided.

  ConditionTruthVal(bool constraint) : Val(constraint) {}

  /// Construct a ConstraintVal indicating the constraint is underconstrained.

  ConditionTruthVal() = default;

  /// \return Stored value, assuming that the value is known.

  /// Crashes otherwise.

  bool getValue() const {

    return *Val;

  }

  /// Return true if the constraint is perfectly constrained to 'true'.

  bool isConstrainedTrue() const { return Val && 
Val.value()46.7k
; }

  /// Return true if the constraint is perfectly constrained to 'false'.

  bool isConstrainedFalse() const { return Val && 
!Val.value()915
; }

  /// Return true if the constrained is perfectly constrained.

  bool isConstrained() const { return Val.has_value(); }

  /// Return true if the constrained is underconstrained and we do not know

  /// if the constraint is true of value.

  bool isUnderconstrained() const { return !Val.has_value(); }

};

class ConstraintManager {

public:

  ConstraintManager() = default;

  virtual ~ConstraintManager();

  virtual bool haveEqualConstraints(ProgramStateRef S1,

                                    ProgramStateRef S2) const = 0;

  ProgramStateRef assume(ProgramStateRef state, DefinedSVal Cond,

                         bool Assumption);

  using ProgramStatePair = std::pair<ProgramStateRef, ProgramStateRef>;

  /// Returns a pair of states (StTrue, StFalse) where the given condition is

  /// assumed to be true or false, respectively.

  /// (Note that these two states might be equal if the parent state turns out

  /// to be infeasible. This may happen if the underlying constraint solver is

  /// not perfectly precise and this may happen very rarely.)

  ProgramStatePair assumeDual(ProgramStateRef State, DefinedSVal Cond);

  ProgramStateRef assumeInclusiveRange(ProgramStateRef State, NonLoc Value,

                                       const llvm::APSInt &From,

                                       const llvm::APSInt &To, bool InBound);

  /// Returns a pair of states (StInRange, StOutOfRange) where the given value

  /// is assumed to be in the range or out of the range, respectively.

  /// (Note that these two states might be equal if the parent state turns out

  /// to be infeasible. This may happen if the underlying constraint solver is

  /// not perfectly precise and this may happen very rarely.)

  ProgramStatePair assumeInclusiveRangeDual(ProgramStateRef State, NonLoc Value,

                                            const llvm::APSInt &From,

                                            const llvm::APSInt &To);

  /// If a symbol is perfectly constrained to a constant, attempt

  /// to return the concrete value.

  ///

  /// Note that a ConstraintManager is not obligated to return a concretized

  /// value for a symbol, even if it is perfectly constrained.

  /// It might return null.

  virtual const llvm::APSInt* getSymVal(ProgramStateRef state,

                                        SymbolRef sym) const {

    return nullptr;

  }

  /// Scan all symbols referenced by the constraints. If the symbol is not

  /// alive, remove it.

  virtual ProgramStateRef removeDeadBindings(ProgramStateRef state,

                                                 SymbolReaper& SymReaper) = 0;

  virtual void printJson(raw_ostream &Out, ProgramStateRef State,

                         const char *NL, unsigned int Space,

                         bool IsDot) const = 0;

  virtual void printValue(raw_ostream &Out, ProgramStateRef State,

                          SymbolRef Sym) {}

  /// Convenience method to query the state to see if a symbol is null or

  /// not null, or if neither assumption can be made.

  ConditionTruthVal isNull(ProgramStateRef State, SymbolRef Sym) {

    return checkNull(State, Sym);

  }

protected:

  /// A helper class to simulate the call stack of nested assume calls.

  class AssumeStackTy {

  public:

    void push(const ProgramState *S) { Aux.push_back(S); }

    void pop() { Aux.pop_back(); }

    bool contains(const ProgramState *S) const {

      return llvm::is_contained(Aux, S);

    }

  private:

    llvm::SmallVector<const ProgramState *, 4> Aux;

  };

  AssumeStackTy AssumeStack;

  virtual ProgramStateRef assumeInternal(ProgramStateRef state,

                                         DefinedSVal Cond, bool Assumption) = 0;

  virtual ProgramStateRef assumeInclusiveRangeInternal(ProgramStateRef State,

                                                       NonLoc Value,

                                                       const llvm::APSInt &From,

                                                       const llvm::APSInt &To,

                                                       bool InBound) = 0;

  /// canReasonAbout - Not all ConstraintManagers can accurately reason about

  ///  all SVal values.  This method returns true if the ConstraintManager can

  ///  reasonably handle a given SVal value.  This is typically queried by

  ///  ExprEngine to determine if the value should be replaced with a

  ///  conjured symbolic value in order to recover some precision.

  virtual bool canReasonAbout(SVal X) const = 0;

  /// Returns whether or not a symbol is known to be null ("true"), known to be

  /// non-null ("false"), or may be either ("underconstrained").

  virtual ConditionTruthVal checkNull(ProgramStateRef State, SymbolRef Sym);

  template <typename AssumeFunction>

  ProgramStatePair assumeDualImpl(ProgramStateRef &State,

                                  AssumeFunction &Assume);

};

std::unique_ptr<ConstraintManager>

CreateRangeConstraintManager(ProgramStateManager &statemgr,

                             ExprEngine *exprengine);

std::unique_ptr<ConstraintManager>

CreateZ3ConstraintManager(ProgramStateManager &statemgr,

                          ExprEngine *exprengine);

} // namespace ento

} // namespace clang

#endif // LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_CONSTRAINTMANAGER_H