GRExprEngine.cpp

  for (NodeSet::iterator I1=S1.begin(), E1=S1.end(); I1 != E1; ++I1) {
    NodeTy* N1 = *I1;
    
    // When getting the value for the LHS, check if we are in an assignment.
    // In such cases, we want to (initially) treat the LHS as an LValue,
    // so we use GetLValue instead of GetValue so that DeclRefExpr's are
    // evaluated to LValueDecl's instead of to an NonLValue.
    const RValue& V1 = 
      B->isAssignmentOp() ? GetLValue(N1->getState(), B->getLHS())
                          : GetValue(N1->getState(), B->getLHS());
    
    NodeSet S2;
    Visit(B->getRHS(), N1, S2);
  
    for (NodeSet::iterator I2=S2.begin(), E2=S2.end(); I2 != E2; ++I2) {

      NodeTy* N2 = *I2;
      StateTy St = N2->getState();
      const RValue& V2 = GetValue(St, B->getRHS());

      BinaryOperator::Opcode Op = B->getOpcode();
      
      if (Op <= BinaryOperator::Or) {
        
        if (isa<UnknownVal>(V1) || isa<UninitializedVal>(V1)) {
          Nodify(Dst, B, N2, SetValue(St, B, V1));
          continue;
        }
        
        if (isa<LValue>(V1)) {
          // FIXME: Add support for RHS being a non-lvalue.
          const LValue& L1 = cast<LValue>(V1);
          const LValue& L2 = cast<LValue>(V2);
          
          Nodify(Dst, B, N2, SetValue(St, B, EvalBinaryOp(ValMgr, Op, L1, L2)));
        }
        else {
          const NonLValue& R1 = cast<NonLValue>(V1);
          const NonLValue& R2 = cast<NonLValue>(V2);
            
          Nodify(Dst, B, N2, SetValue(St, B, EvalBinaryOp(ValMgr, Op, R1, R2)));
        }
        
        continue;
      
      }
      
      switch (Op) {
        case BinaryOperator::Assign: {
          const LValue& L1 = cast<LValue>(V1);
          Nodify(Dst, B, N2, SetValue(SetValue(St, B, V2), L1, V2));
          break;
        }

        default: { // Compound assignment operators.
          
          assert (B->isCompoundAssignmentOp());
                          
          const LValue& L1 = cast<LValue>(V1);
          RValue Result = cast<NonLValue>(UnknownVal());
          
          if (Op >= BinaryOperator::AndAssign)
            ((int&) Op) -= (BinaryOperator::AndAssign - BinaryOperator::And);
          else
            ((int&) Op) -= BinaryOperator::MulAssign;
          
          if (isa<LValue>(V2)) {
            // FIXME: Add support for Non-LValues on RHS.
            const LValue& L2 = cast<LValue>(V2);
            Result = EvalBinaryOp(ValMgr, Op, L1, L2);
          }
          else {
            const NonLValue& R1 = cast<NonLValue>(GetValue(N1->getState(), L1));
            const NonLValue& R2 = cast<NonLValue>(V2);
            Result = EvalBinaryOp(ValMgr, Op, R1, R2);
          }
          
          Nodify(Dst, B, N2, SetValue(SetValue(St, B, Result), L1, Result));
          break;
        }
      }
    }
  }
}


void GRExprEngine::Visit(Stmt* S, GRExprEngine::NodeTy* Pred,
                        GRExprEngine::NodeSet& Dst) {

  // FIXME: add metadata to the CFG so that we can disable
  //  this check when we KNOW that there is no block-level subexpression.
  //  The motivation is that this check requires a hashtable lookup.

  if (S != CurrentStmt && getCFG().isBlkExpr(S)) {
    Dst.Add(Pred);
    return;
  }

  switch (S->getStmtClass()) {
      
    default:
      // Cases we intentionally have "default" handle:
      //   AddrLabelExpr, CharacterLiteral, IntegerLiteral
      
      Dst.Add(Pred); // No-op. Simply propagate the current state unchanged.
      break;
                                                       
    case Stmt::BinaryOperatorClass: {
      BinaryOperator* B = cast<BinaryOperator>(S);
 
      if (B->isLogicalOp()) {
        VisitLogicalExpr(B, Pred, Dst);
        break;
      }
      else if (B->getOpcode() == BinaryOperator::Comma) {
        StateTy St = Pred->getState();
        Nodify(Dst, B, Pred, SetValue(St, B, GetValue(St, B->getRHS())));
        break;
      }
      
      VisitBinaryOperator(cast<BinaryOperator>(S), Pred, Dst);
      break;
    }

    case Stmt::CastExprClass: {
      CastExpr* C = cast<CastExpr>(S);
      VisitCast(C, C->getSubExpr(), Pred, Dst);
      break;
    }
      
    case Stmt::ChooseExprClass: { // __builtin_choose_expr
      ChooseExpr* C = cast<ChooseExpr>(S);
      VisitGuardedExpr(C, C->getLHS(), C->getRHS(), Pred, Dst);
      break;
    }
      
    case Stmt::CompoundAssignOperatorClass:
      VisitBinaryOperator(cast<BinaryOperator>(S), Pred, Dst);
      break;
      
    case Stmt::ConditionalOperatorClass: { // '?' operator
      ConditionalOperator* C = cast<ConditionalOperator>(S);
      VisitGuardedExpr(C, C->getLHS(), C->getRHS(), Pred, Dst);
      break;
    }
      
    case Stmt::DeclRefExprClass:
      VisitDeclRefExpr(cast<DeclRefExpr>(S), Pred, Dst);
      break;
      
    case Stmt::DeclStmtClass:
      VisitDeclStmt(cast<DeclStmt>(S), Pred, Dst);
      break;
      
    case Stmt::ImplicitCastExprClass: {
      ImplicitCastExpr* C = cast<ImplicitCastExpr>(S);
      VisitCast(C, C->getSubExpr(), Pred, Dst);
      break;
    }

    case Stmt::ParenExprClass:
      Visit(cast<ParenExpr>(S)->getSubExpr(), Pred, Dst);
      break;
      
    case Stmt::SizeOfAlignOfTypeExprClass:
      VisitSizeOfAlignOfTypeExpr(cast<SizeOfAlignOfTypeExpr>(S), Pred, Dst);
      break;
      
    case Stmt::StmtExprClass: {
      StmtExpr* SE = cast<StmtExpr>(S);
      
      StateTy St = Pred->getState();
      Expr* LastExpr = cast<Expr>(*SE->getSubStmt()->body_rbegin());
      Nodify(Dst, SE, Pred, SetValue(St, SE, GetValue(St, LastExpr)));
      break;      
    }
      
    case Stmt::ReturnStmtClass: {
      if (Expr* R = cast<ReturnStmt>(S)->getRetValue())
        Visit(R, Pred, Dst);
      else
        Dst.Add(Pred);
      
      break;
    }
      
    case Stmt::UnaryOperatorClass:
      VisitUnaryOperator(cast<UnaryOperator>(S), Pred, Dst);
      break;
  }
}

//===----------------------------------------------------------------------===//
// "Assume" logic.
//===----------------------------------------------------------------------===//

GRExprEngine::StateTy GRExprEngine::Assume(StateTy St, LValue Cond,
                                         bool Assumption, 
                                         bool& isFeasible) {    
  
  switch (Cond.getSubKind()) {
    default:
      assert (false && "'Assume' not implemented for this LValue.");
      return St;
      
    case lval::SymbolValKind:
      if (Assumption)
        return AssumeSymNE(St, cast<lval::SymbolVal>(Cond).getSymbol(),
                           ValMgr.getZeroWithPtrWidth(), isFeasible);
      else
        return AssumeSymEQ(St, cast<lval::SymbolVal>(Cond).getSymbol(),
                           ValMgr.getZeroWithPtrWidth(), isFeasible);
      
      
    case lval::DeclValKind:
      isFeasible = Assumption;
      return St;

    case lval::ConcreteIntKind: {
      bool b = cast<lval::ConcreteInt>(Cond).getValue() != 0;
      isFeasible = b ? Assumption : !Assumption;      
      return St;
    }
  }
}

GRExprEngine::StateTy GRExprEngine::Assume(StateTy St, NonLValue Cond,
                                         bool Assumption, 
                                         bool& isFeasible) {
  
  switch (Cond.getSubKind()) {
    default:
      assert (false && "'Assume' not implemented for this NonLValue.");
      return St;
      
      
    case nonlval::SymbolValKind: {
      nonlval::SymbolVal& SV = cast<nonlval::SymbolVal>(Cond);
      SymbolID sym = SV.getSymbol();
      
      if (Assumption)
        return AssumeSymNE(St, sym, ValMgr.getValue(0, SymMgr.getType(sym)),
                           isFeasible);
      else
        return AssumeSymEQ(St, sym, ValMgr.getValue(0, SymMgr.getType(sym)),
                           isFeasible);
    }
      
    case nonlval::SymIntConstraintValKind:
      return
        AssumeSymInt(St, Assumption,
                     cast<nonlval::SymIntConstraintVal>(Cond).getConstraint(),
                     isFeasible);
      
    case nonlval::ConcreteIntKind: {
      bool b = cast<nonlval::ConcreteInt>(Cond).getValue() != 0;
      isFeasible = b ? Assumption : !Assumption;      
      return St;
    }
  }
}

GRExprEngine::StateTy
GRExprEngine::AssumeSymNE(StateTy St, SymbolID sym,
                         const llvm::APSInt& V, bool& isFeasible) {

  // First, determine if sym == X, where X != V.
  if (const llvm::APSInt* X = St.getSymVal(sym)) {
    isFeasible = *X != V;
    return St;
  }
  
  // Second, determine if sym != V.
  if (St.isNotEqual(sym, V)) {
    isFeasible = true;
    return St;
  }
      
  // If we reach here, sym is not a constant and we don't know if it is != V.
  // Make that assumption.
  
  isFeasible = true;
  return StateMgr.AddNE(St, sym, V);
}

GRExprEngine::StateTy
GRExprEngine::AssumeSymEQ(StateTy St, SymbolID sym,
                         const llvm::APSInt& V, bool& isFeasible) {
  
  // First, determine if sym == X, where X != V.
  if (const llvm::APSInt* X = St.getSymVal(sym)) {
    isFeasible = *X == V;
    return St;
  }
  
  // Second, determine if sym != V.
  if (St.isNotEqual(sym, V)) {
    isFeasible = false;
    return St;
  }
  
  // If we reach here, sym is not a constant and we don't know if it is == V.
  // Make that assumption.
  
  isFeasible = true;
  return StateMgr.AddEQ(St, sym, V);
}

GRExprEngine::StateTy
GRExprEngine::AssumeSymInt(StateTy St, bool Assumption,
                          const SymIntConstraint& C, bool& isFeasible) {
  
  switch (C.getOpcode()) {
    default:
      // No logic yet for other operators.
      return St;
      
    case BinaryOperator::EQ:
      if (Assumption)
        return AssumeSymEQ(St, C.getSymbol(), C.getInt(), isFeasible);
      else
        return AssumeSymNE(St, C.getSymbol(), C.getInt(), isFeasible);
      
    case BinaryOperator::NE:
      if (Assumption)
        return AssumeSymNE(St, C.getSymbol(), C.getInt(), isFeasible);
      else
        return AssumeSymEQ(St, C.getSymbol(), C.getInt(), isFeasible);
  }
}

//===----------------------------------------------------------------------===//
// Driver.
//===----------------------------------------------------------------------===//

#ifndef NDEBUG
static GRExprEngine* GraphPrintCheckerState;

namespace llvm {
template<>
struct VISIBILITY_HIDDEN DOTGraphTraits<GRExprEngine::NodeTy*> :
  public DefaultDOTGraphTraits {
    
  static void PrintVarBindings(std::ostream& Out, GRExprEngine::StateTy St) {

    Out << "Variables:\\l";
    
    bool isFirst = true;
    
    for (GRExprEngine::StateTy::vb_iterator I=St.vb_begin(),
                                           E=St.vb_end(); I!=E;++I) {        

      if (isFirst)
        isFirst = false;
      else
        Out << "\\l";
      
      Out << ' ' << I.getKey()->getName() << " : ";
      I.getData().print(Out);
    }
    
  }
    
    
  static void PrintSubExprBindings(std::ostream& Out, GRExprEngine::StateTy St){
    
    bool isFirst = true;
    
    for (GRExprEngine::StateTy::seb_iterator I=St.seb_begin(), E=St.seb_end();
                                            I != E;++I) {        
      
      if (isFirst) {
        Out << "\\l\\lSub-Expressions:\\l";
        isFirst = false;
      }
      else
        Out << "\\l";
      
      Out << " (" << (void*) I.getKey() << ") ";
      I.getKey()->printPretty(Out);
      Out << " : ";
      I.getData().print(Out);
    }
  }
    
  static void PrintBlkExprBindings(std::ostream& Out, GRExprEngine::StateTy St){
        
    bool isFirst = true;

    for (GRExprEngine::StateTy::beb_iterator I=St.beb_begin(), E=St.beb_end();
                                            I != E; ++I) {      
      if (isFirst) {
        Out << "\\l\\lBlock-level Expressions:\\l";
        isFirst = false;
      }
      else
        Out << "\\l";

      Out << " (" << (void*) I.getKey() << ") ";
      I.getKey()->printPretty(Out);
      Out << " : ";
      I.getData().print(Out);
    }
  }
    
  static void PrintEQ(std::ostream& Out, GRExprEngine::StateTy St) {
    ValueState::ConstantEqTy CE = St.getImpl()->ConstantEq;
    
    if (CE.isEmpty())
      return;
    
    Out << "\\l\\|'==' constraints:";

    for (ValueState::ConstantEqTy::iterator I=CE.begin(), E=CE.end(); I!=E;++I)
      Out << "\\l $" << I.getKey() << " : " << I.getData()->toString();
  }
    
  static void PrintNE(std::ostream& Out, GRExprEngine::StateTy St) {
    ValueState::ConstantNotEqTy NE = St.getImpl()->ConstantNotEq;
    
    if (NE.isEmpty())
      return;
    
    Out << "\\l\\|'!=' constraints:";
    
    for (ValueState::ConstantNotEqTy::iterator I=NE.begin(), EI=NE.end();
         I != EI; ++I){
      
      Out << "\\l $" << I.getKey() << " : ";
      bool isFirst = true;
      
      ValueState::IntSetTy::iterator J=I.getData().begin(),
                                    EJ=I.getData().end();      
      for ( ; J != EJ; ++J) {        
        if (isFirst) isFirst = false;
        else Out << ", ";
        
        Out << (*J)->toString();
      }    
    }
  }    
    
  static std::string getNodeLabel(const GRExprEngine::NodeTy* N, void*) {
    std::ostringstream Out;

    // Program Location.
    ProgramPoint Loc = N->getLocation();
    
    switch (Loc.getKind()) {
      case ProgramPoint::BlockEntranceKind:
        Out << "Block Entrance: B" 
            << cast<BlockEntrance>(Loc).getBlock()->getBlockID();
        break;
      
      case ProgramPoint::BlockExitKind:
        assert (false);
        break;
        
      case ProgramPoint::PostStmtKind: {
        const PostStmt& L = cast<PostStmt>(Loc);
        Out << L.getStmt()->getStmtClassName() << ':' 
            << (void*) L.getStmt() << ' ';
        
        L.getStmt()->printPretty(Out);
        
        if (GraphPrintCheckerState->isImplicitNullDeref(N)) {
          Out << "\\|Implicit-Null Dereference.\\l";
        }
        else if (GraphPrintCheckerState->isExplicitNullDeref(N)) {
          Out << "\\|Explicit-Null Dereference.\\l";
        }
        
        break;
      }
    
      default: {
        const BlockEdge& E = cast<BlockEdge>(Loc);
        Out << "Edge: (B" << E.getSrc()->getBlockID() << ", B"
            << E.getDst()->getBlockID()  << ')';
        
        if (Stmt* T = E.getSrc()->getTerminator()) {
          Out << "\\|Terminator: ";
          E.getSrc()->printTerminator(Out);
          
          if (isa<SwitchStmt>(T)) {
            Stmt* Label = E.getDst()->getLabel();
            
            if (Label) {                        
              if (CaseStmt* C = dyn_cast<CaseStmt>(Label)) {
                Out << "\\lcase ";
                C->getLHS()->printPretty(Out);
                
                if (Stmt* RHS = C->getRHS()) {
                  Out << " .. ";
                  RHS->printPretty(Out);
                }
                
                Out << ":";
              }
              else {
                assert (isa<DefaultStmt>(Label));
                Out << "\\ldefault:";
              }
            }
            else 
              Out << "\\l(implicit) default:";
          }
          else if (isa<IndirectGotoStmt>(T)) {
            // FIXME
          }
          else {
            Out << "\\lCondition: ";
            if (*E.getSrc()->succ_begin() == E.getDst())
              Out << "true";
            else
              Out << "false";                        
          }
          
          Out << "\\l";
        }
        
        if (GraphPrintCheckerState->isUninitControlFlow(N)) {
          Out << "\\|Control-flow based on\\lUninitialized value.\\l";
        }
      }
    }
    
    Out << "\\|StateID: " << (void*) N->getState().getImpl() << "\\|";

    N->getState().printDOT(Out);
      
    Out << "\\l";
    return Out.str();
  }
};
} // end llvm namespace    
#endif

namespace clang {
void RunGRConstants(CFG& cfg, FunctionDecl& FD, ASTContext& Ctx,
                    Diagnostic& Diag) {
  
  GRCoreEngine<GRExprEngine> Engine(cfg, FD, Ctx);
  GRExprEngine* CheckerState = &Engine.getCheckerState();
  
  // Execute the worklist algorithm.
  Engine.ExecuteWorkList();
  
  // Look for explicit-Null dereferences and warn about them.

  
  for (GRExprEngine::null_iterator I=CheckerState->null_begin(),
                                  E=CheckerState->null_end(); I!=E; ++I) {
    
    const PostStmt& L = cast<PostStmt>((*I)->getLocation());
    Expr* E = cast<Expr>(L.getStmt());
    
    Diag.Report(FullSourceLoc(E->getExprLoc(), Ctx.getSourceManager()),
                diag::chkr_null_deref_after_check);
  }
  
  
#ifndef NDEBUG
  GraphPrintCheckerState = CheckerState;
  llvm::ViewGraph(*Engine.getGraph().roots_begin(),"GRExprEngine");
  GraphPrintCheckerState = NULL;
#endif  
}
} // end clang namespace