clang/lib/StaticAnalyzer/Core/ExprEngine.cpp

//=-- ExprEngine.cpp - Path-Sensitive Expression-Level Dataflow ---*- C++ -*-=
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
//  This file defines a meta-engine for path-sensitive dataflow analysis that
//  is built on GREngine, but provides the boilerplate to execute transfer
//  functions and build the ExplodedGraph at the expression level.
//
//===----------------------------------------------------------------------===//

#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ObjCMessage.h"
#include "clang/AST/CharUnits.h"
#include "clang/AST/ParentMap.h"
#include "clang/AST/StmtObjC.h"
#include "clang/AST/DeclCXX.h"
#include "clang/Basic/Builtins.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/PrettyStackTrace.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/ImmutableList.h"

#ifndef NDEBUG
#include "llvm/Support/GraphWriter.h"
#endif

using namespace clang;
using namespace ento;
using llvm::APSInt;

//===----------------------------------------------------------------------===//
// Utility functions.
//===----------------------------------------------------------------------===//

static inline Selector GetNullarySelector(const char* name, ASTContext &Ctx) {
  IdentifierInfo* II = &Ctx.Idents.get(name);
  return Ctx.Selectors.getSelector(0, &II);
}

//===----------------------------------------------------------------------===//
// Engine construction and deletion.
//===----------------------------------------------------------------------===//

ExprEngine::ExprEngine(AnalysisManager &mgr, bool gcEnabled)
  : AMgr(mgr),
    AnalysisDeclContexts(mgr.getAnalysisDeclContextManager()),
    Engine(*this),
    G(Engine.getGraph()),
    StateMgr(getContext(), mgr.getStoreManagerCreator(),
             mgr.getConstraintManagerCreator(), G.getAllocator(),
             *this),
    SymMgr(StateMgr.getSymbolManager()),
    svalBuilder(StateMgr.getSValBuilder()),
    EntryNode(NULL),
    currentStmt(NULL), currentStmtIdx(0), currentBuilderContext(0),
    NSExceptionII(NULL), NSExceptionInstanceRaiseSelectors(NULL),
    RaiseSel(GetNullarySelector("raise", getContext())),
    ObjCGCEnabled(gcEnabled), BR(mgr, *this) {
  
  if (mgr.shouldEagerlyTrimExplodedGraph()) {
    // Enable eager node reclaimation when constructing the ExplodedGraph.  
    G.enableNodeReclamation();
  }
}

ExprEngine::~ExprEngine() {
  BR.FlushReports();
  delete [] NSExceptionInstanceRaiseSelectors;
}

//===----------------------------------------------------------------------===//
// Utility methods.
//===----------------------------------------------------------------------===//

ProgramStateRef ExprEngine::getInitialState(const LocationContext *InitLoc) {
  ProgramStateRef state = StateMgr.getInitialState(InitLoc);
  const Decl *D = InitLoc->getDecl();

  // Preconditions.
  // FIXME: It would be nice if we had a more general mechanism to add
  // such preconditions.  Some day.
  do {

    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
      // Precondition: the first argument of 'main' is an integer guaranteed
      //  to be > 0.
      const IdentifierInfo *II = FD->getIdentifier();
      if (!II || !(II->getName() == "main" && FD->getNumParams() > 0))
        break;

      const ParmVarDecl *PD = FD->getParamDecl(0);
      QualType T = PD->getType();
      if (!T->isIntegerType())
        break;

      const MemRegion *R = state->getRegion(PD, InitLoc);
      if (!R)
        break;

      SVal V = state->getSVal(loc::MemRegionVal(R));
      SVal Constraint_untested = evalBinOp(state, BO_GT, V,
                                           svalBuilder.makeZeroVal(T),
                                           getContext().IntTy);

      DefinedOrUnknownSVal *Constraint =
        dyn_cast<DefinedOrUnknownSVal>(&Constraint_untested);

      if (!Constraint)
        break;

      if (ProgramStateRef newState = state->assume(*Constraint, true))
        state = newState;
    }
    break;
  }
  while (0);

  if (const ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
    // Precondition: 'self' is always non-null upon entry to an Objective-C
    // method.
    const ImplicitParamDecl *SelfD = MD->getSelfDecl();
    const MemRegion *R = state->getRegion(SelfD, InitLoc);
    SVal V = state->getSVal(loc::MemRegionVal(R));

    if (const Loc *LV = dyn_cast<Loc>(&V)) {
      // Assume that the pointer value in 'self' is non-null.
      state = state->assume(*LV, true);
      assert(state && "'self' cannot be null");
    }
  }

  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(D)) {
    if (!MD->isStatic()) {
      // Precondition: 'this' is always non-null upon entry to the
      // top-level function.  This is our starting assumption for
      // analyzing an "open" program.
      const StackFrameContext *SFC = InitLoc->getCurrentStackFrame();
      if (SFC->getParent() == 0) {
        loc::MemRegionVal L(getCXXThisRegion(MD, SFC));
        SVal V = state->getSVal(L);
        if (const Loc *LV = dyn_cast<Loc>(&V)) {
          state = state->assume(*LV, true);
          assert(state && "'this' cannot be null");
        }
      }
    }
  }
    
  return state;
}

//===----------------------------------------------------------------------===//
// Top-level transfer function logic (Dispatcher).
//===----------------------------------------------------------------------===//

/// evalAssume - Called by ConstraintManager. Used to call checker-specific
///  logic for handling assumptions on symbolic values.
ProgramStateRef ExprEngine::processAssume(ProgramStateRef state,
                                              SVal cond, bool assumption) {
  return getCheckerManager().runCheckersForEvalAssume(state, cond, assumption);
}

bool ExprEngine::wantsRegionChangeUpdate(ProgramStateRef state) {
  return getCheckerManager().wantsRegionChangeUpdate(state);
}

ProgramStateRef 
ExprEngine::processRegionChanges(ProgramStateRef state,
                            const StoreManager::InvalidatedSymbols *invalidated,
                                 ArrayRef<const MemRegion *> Explicits,
                                 ArrayRef<const MemRegion *> Regions) {
  return getCheckerManager().runCheckersForRegionChanges(state, invalidated,
                                                         Explicits, Regions);
}

void ExprEngine::printState(raw_ostream &Out, ProgramStateRef State,
                            const char *NL, const char *Sep) {
  getCheckerManager().runCheckersForPrintState(Out, State, NL, Sep);
}

void ExprEngine::processEndWorklist(bool hasWorkRemaining) {
  getCheckerManager().runCheckersForEndAnalysis(G, BR, *this);
}

void ExprEngine::processCFGElement(const CFGElement E, ExplodedNode *Pred,
                                   unsigned StmtIdx, NodeBuilderContext *Ctx) {
  currentStmtIdx = StmtIdx;
  currentBuilderContext = Ctx;

  switch (E.getKind()) {
    case CFGElement::Invalid:
      llvm_unreachable("Unexpected CFGElement kind.");
    case CFGElement::Statement:
      ProcessStmt(const_cast<Stmt*>(E.getAs<CFGStmt>()->getStmt()), Pred);
      return;
    case CFGElement::Initializer:
      ProcessInitializer(E.getAs<CFGInitializer>()->getInitializer(), Pred);
      return;
    case CFGElement::AutomaticObjectDtor:
    case CFGElement::BaseDtor:
    case CFGElement::MemberDtor:
    case CFGElement::TemporaryDtor:
      ProcessImplicitDtor(*E.getAs<CFGImplicitDtor>(), Pred);
      return;
  }
}

static bool shouldRemoveDeadBindings(AnalysisManager &AMgr,
                                     const CFGStmt S,
                                     const ExplodedNode *Pred,
                                     const LocationContext *LC) {
  
  // Are we never purging state values?
  if (AMgr.getPurgeMode() == PurgeNone)
    return false;

  // Is this the beginning of a basic block?
  if (isa<BlockEntrance>(Pred->getLocation()))
    return true;

  // Is this on a non-expression?
  if (!isa<Expr>(S.getStmt()))
    return true;
  
  // Is this an expression that is consumed by another expression?  If so,
  // postpone cleaning out the state.
  ParentMap &PM = LC->getAnalysisDeclContext()->getParentMap();
  return !PM.isConsumedExpr(cast<Expr>(S.getStmt()));
}

void ExprEngine::ProcessStmt(const CFGStmt S,
                             ExplodedNode *Pred) {
  // Reclaim any unnecessary nodes in the ExplodedGraph.
  G.reclaimRecentlyAllocatedNodes();
  
  currentStmt = S.getStmt();
  PrettyStackTraceLoc CrashInfo(getContext().getSourceManager(),
                                currentStmt->getLocStart(),
                                "Error evaluating statement");

  EntryNode = Pred;

  ProgramStateRef EntryState = EntryNode->getState();
  CleanedState = EntryState;

  // Create the cleaned state.
  const LocationContext *LC = EntryNode->getLocationContext();
  SymbolReaper SymReaper(LC, currentStmt, SymMgr, getStoreManager());

  if (shouldRemoveDeadBindings(AMgr, S, Pred, LC)) {
    getCheckerManager().runCheckersForLiveSymbols(CleanedState, SymReaper);

    const StackFrameContext *SFC = LC->getCurrentStackFrame();

    // Create a state in which dead bindings are removed from the environment
    // and the store. TODO: The function should just return new env and store,
    // not a new state.
    CleanedState = StateMgr.removeDeadBindings(CleanedState, SFC, SymReaper);
  }

  // Process any special transfer function for dead symbols.
  ExplodedNodeSet Tmp;
  // A tag to track convenience transitions, which can be removed at cleanup.
  static SimpleProgramPointTag cleanupTag("ExprEngine : Clean Node");

  if (!SymReaper.hasDeadSymbols()) {
    // Generate a CleanedNode that has the environment and store cleaned
    // up. Since no symbols are dead, we can optimize and not clean out
    // the constraint manager.
    StmtNodeBuilder Bldr(Pred, Tmp, *currentBuilderContext);
    Bldr.generateNode(currentStmt, EntryNode, CleanedState, false, &cleanupTag);

  } else {
    // Call checkers with the non-cleaned state so that they could query the
    // values of the soon to be dead symbols.
    ExplodedNodeSet CheckedSet;
    getCheckerManager().runCheckersForDeadSymbols(CheckedSet, EntryNode,
                                                 SymReaper, currentStmt, *this);

    // For each node in CheckedSet, generate CleanedNodes that have the
    // environment, the store, and the constraints cleaned up but have the
    // user-supplied states as the predecessors.
    StmtNodeBuilder Bldr(CheckedSet, Tmp, *currentBuilderContext);
    for (ExplodedNodeSet::const_iterator
          I = CheckedSet.begin(), E = CheckedSet.end(); I != E; ++I) {
      ProgramStateRef CheckerState = (*I)->getState();

      // The constraint manager has not been cleaned up yet, so clean up now.
      CheckerState = getConstraintManager().removeDeadBindings(CheckerState,
                                                               SymReaper);

      assert(StateMgr.haveEqualEnvironments(CheckerState, EntryState) &&
        "Checkers are not allowed to modify the Environment as a part of "
        "checkDeadSymbols processing.");
      assert(StateMgr.haveEqualStores(CheckerState, EntryState) &&
        "Checkers are not allowed to modify the Store as a part of "
        "checkDeadSymbols processing.");

      // Create a state based on CleanedState with CheckerState GDM and
      // generate a transition to that state.
      ProgramStateRef CleanedCheckerSt =
        StateMgr.getPersistentStateWithGDM(CleanedState, CheckerState);
      Bldr.generateNode(currentStmt, *I, CleanedCheckerSt, false, &cleanupTag,
                        ProgramPoint::PostPurgeDeadSymbolsKind);
    }
  }

  ExplodedNodeSet Dst;
  for (ExplodedNodeSet::iterator I=Tmp.begin(), E=Tmp.end(); I!=E; ++I) {
    ExplodedNodeSet DstI;
    // Visit the statement.
    Visit(currentStmt, *I, DstI);
    Dst.insert(DstI);
  }

  // Enqueue the new nodes onto the work list.
  Engine.enqueue(Dst, currentBuilderContext->getBlock(), currentStmtIdx);

  // NULL out these variables to cleanup.
  CleanedState = NULL;
  EntryNode = NULL;
  currentStmt = 0;
}

void ExprEngine::ProcessInitializer(const CFGInitializer Init,
                                    ExplodedNode *Pred) {
  ExplodedNodeSet Dst;

  // We don't set EntryNode and currentStmt. And we don't clean up state.
  const CXXCtorInitializer *BMI = Init.getInitializer();
  const StackFrameContext *stackFrame =
                           cast<StackFrameContext>(Pred->getLocationContext());
  const CXXConstructorDecl *decl =
                           cast<CXXConstructorDecl>(stackFrame->getDecl());
  const CXXThisRegion *thisReg = getCXXThisRegion(decl, stackFrame);

  SVal thisVal = Pred->getState()->getSVal(thisReg);

  if (BMI->isAnyMemberInitializer()) {
    ExplodedNodeSet AfterEval;

    // Evaluate the initializer.
    Visit(BMI->getInit(), Pred, AfterEval);

    StmtNodeBuilder Bldr(AfterEval, Dst, *currentBuilderContext);
    for (ExplodedNodeSet::iterator I = AfterEval.begin(),
                                   E = AfterEval.end(); I != E; ++I){
      ExplodedNode *P = *I;
      ProgramStateRef state = P->getState();

      const FieldDecl *FD = BMI->getAnyMember();

      SVal FieldLoc = state->getLValue(FD, thisVal);
      SVal InitVal = state->getSVal(BMI->getInit(), Pred->getLocationContext());
      state = state->bindLoc(FieldLoc, InitVal);

      // Use a custom node building process.
      PostInitializer PP(BMI, stackFrame);
      // Builder automatically add the generated node to the deferred set,
      // which are processed in the builder's dtor.
      Bldr.generateNode(PP, P, state);
    }
  } else {
    assert(BMI->isBaseInitializer());

    // Get the base class declaration.
    const CXXConstructExpr *ctorExpr = cast<CXXConstructExpr>(BMI->getInit());

    // Create the base object region.
    SVal baseVal =
        getStoreManager().evalDerivedToBase(thisVal, ctorExpr->getType());
    const MemRegion *baseReg = baseVal.getAsRegion();
    assert(baseReg);

    VisitCXXConstructExpr(ctorExpr, baseReg, Pred, Dst);
  }

  // Enqueue the new nodes onto the work list.
  Engine.enqueue(Dst, currentBuilderContext->getBlock(), currentStmtIdx);
}

void ExprEngine::ProcessImplicitDtor(const CFGImplicitDtor D,
                                     ExplodedNode *Pred) {
  ExplodedNodeSet Dst;
  switch (D.getKind()) {
  case CFGElement::AutomaticObjectDtor:
    ProcessAutomaticObjDtor(cast<CFGAutomaticObjDtor>(D), Pred, Dst);
    break;
  case CFGElement::BaseDtor:
    ProcessBaseDtor(cast<CFGBaseDtor>(D), Pred, Dst);
    break;
  case CFGElement::MemberDtor:
    ProcessMemberDtor(cast<CFGMemberDtor>(D), Pred, Dst);
    break;
  case CFGElement::TemporaryDtor:
    ProcessTemporaryDtor(cast<CFGTemporaryDtor>(D), Pred, Dst);
    break;
  default:
    llvm_unreachable("Unexpected dtor kind.");
  }

  // Enqueue the new nodes onto the work list.
  Engine.enqueue(Dst, currentBuilderContext->getBlock(), currentStmtIdx);
}

void ExprEngine::ProcessAutomaticObjDtor(const CFGAutomaticObjDtor Dtor,
                                         ExplodedNode *Pred,
                                         ExplodedNodeSet &Dst) {
  ProgramStateRef state = Pred->getState();
  const VarDecl *varDecl = Dtor.getVarDecl();

  QualType varType = varDecl->getType();

  if (const ReferenceType *refType = varType->getAs<ReferenceType>())
    varType = refType->getPointeeType();

  const CXXRecordDecl *recordDecl = varType->getAsCXXRecordDecl();
  assert(recordDecl && "get CXXRecordDecl fail");
  const CXXDestructorDecl *dtorDecl = recordDecl->getDestructor();

  Loc dest = state->getLValue(varDecl, Pred->getLocationContext());

  VisitCXXDestructor(dtorDecl, cast<loc::MemRegionVal>(dest).getRegion(),
                     Dtor.getTriggerStmt(), Pred, Dst);
}

void ExprEngine::ProcessBaseDtor(const CFGBaseDtor D,
                                 ExplodedNode *Pred, ExplodedNodeSet &Dst) {}

void ExprEngine::ProcessMemberDtor(const CFGMemberDtor D,
                                   ExplodedNode *Pred, ExplodedNodeSet &Dst) {}

void ExprEngine::ProcessTemporaryDtor(const CFGTemporaryDtor D,
                                      ExplodedNode *Pred,
                                      ExplodedNodeSet &Dst) {}

void ExprEngine::Visit(const Stmt *S, ExplodedNode *Pred, 
                       ExplodedNodeSet &DstTop) {
  PrettyStackTraceLoc CrashInfo(getContext().getSourceManager(),
                                S->getLocStart(),
                                "Error evaluating statement");
  ExplodedNodeSet Dst;
  StmtNodeBuilder Bldr(Pred, DstTop, *currentBuilderContext);

  // Expressions to ignore.
  if (const Expr *Ex = dyn_cast<Expr>(S))
    S = Ex->IgnoreParens();
  
  // 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 && Pred->getLocationContext()->getCFG()->isBlkExpr(S))
    return;

  switch (S->getStmtClass()) {
    // C++ and ARC stuff we don't support yet.
    case Expr::ObjCIndirectCopyRestoreExprClass:
    case Stmt::CXXBindTemporaryExprClass:
    case Stmt::CXXCatchStmtClass:
    case Stmt::CXXDependentScopeMemberExprClass:
    case Stmt::CXXPseudoDestructorExprClass:
    case Stmt::CXXThrowExprClass:
    case Stmt::CXXTryStmtClass:
    case Stmt::CXXTypeidExprClass:
    case Stmt::CXXUuidofExprClass:
    case Stmt::CXXUnresolvedConstructExprClass:
    case Stmt::CXXScalarValueInitExprClass:
    case Stmt::DependentScopeDeclRefExprClass:
    case Stmt::UnaryTypeTraitExprClass:
    case Stmt::BinaryTypeTraitExprClass:
    case Stmt::ArrayTypeTraitExprClass:
    case Stmt::ExpressionTraitExprClass:
    case Stmt::UnresolvedLookupExprClass:
    case Stmt::UnresolvedMemberExprClass:
    case Stmt::CXXNoexceptExprClass:
    case Stmt::PackExpansionExprClass:
    case Stmt::SubstNonTypeTemplateParmPackExprClass:
    case Stmt::SEHTryStmtClass:
    case Stmt::SEHExceptStmtClass:
    case Stmt::SEHFinallyStmtClass: {
      const ExplodedNode *node = Bldr.generateNode(S, Pred, Pred->getState());
      Engine.addAbortedBlock(node, currentBuilderContext->getBlock());
      break;
    }
    
    // We don't handle default arguments either yet, but we can fake it
    // for now by just skipping them.
    case Stmt::SubstNonTypeTemplateParmExprClass:
    case Stmt::CXXDefaultArgExprClass:
      break;

    case Stmt::ParenExprClass:
      llvm_unreachable("ParenExprs already handled.");
    case Stmt::GenericSelectionExprClass:
      llvm_unreachable("GenericSelectionExprs already handled.");
    // Cases that should never be evaluated simply because they shouldn't
    // appear in the CFG.
    case Stmt::BreakStmtClass:
    case Stmt::CaseStmtClass:
    case Stmt::CompoundStmtClass:
    case Stmt::ContinueStmtClass:
    case Stmt::CXXForRangeStmtClass:
    case Stmt::DefaultStmtClass:
    case Stmt::DoStmtClass:
    case Stmt::ForStmtClass:
    case Stmt::GotoStmtClass:
    case Stmt::IfStmtClass:
    case Stmt::IndirectGotoStmtClass:
    case Stmt::LabelStmtClass:
    case Stmt::NoStmtClass:
    case Stmt::NullStmtClass:
    case Stmt::SwitchStmtClass:
    case Stmt::WhileStmtClass:
    case Expr::MSDependentExistsStmtClass:
      llvm_unreachable("Stmt should not be in analyzer evaluation loop");

    case Stmt::GNUNullExprClass: {
      // GNU __null is a pointer-width integer, not an actual pointer.
      ProgramStateRef state = Pred->getState();
      state = state->BindExpr(S, Pred->getLocationContext(),
                              svalBuilder.makeIntValWithPtrWidth(0, false));
      Bldr.generateNode(S, Pred, state);
      break;
    }

    case Stmt::ObjCAtSynchronizedStmtClass:
      Bldr.takeNodes(Pred);
      VisitObjCAtSynchronizedStmt(cast<ObjCAtSynchronizedStmt>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::ObjCPropertyRefExprClass:
      // Implicitly handled by Environment::getSVal().
      break;

    case Stmt::ImplicitValueInitExprClass: {
      ProgramStateRef state = Pred->getState();
      QualType ty = cast<ImplicitValueInitExpr>(S)->getType();
      SVal val = svalBuilder.makeZeroVal(ty);
      Bldr.generateNode(S, Pred, state->BindExpr(S, Pred->getLocationContext(),
                                                 val));
      break;
    }
      
    case Stmt::ExprWithCleanupsClass:
      Bldr.takeNodes(Pred);
      Visit(cast<ExprWithCleanups>(S)->getSubExpr(), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    // Cases not handled yet; but will handle some day.
    case Stmt::DesignatedInitExprClass:
    case Stmt::ExtVectorElementExprClass:
    case Stmt::ImaginaryLiteralClass:
    case Stmt::ObjCAtCatchStmtClass:
    case Stmt::ObjCAtFinallyStmtClass:
    case Stmt::ObjCAtTryStmtClass:
    case Stmt::ObjCAutoreleasePoolStmtClass:
    case Stmt::ObjCEncodeExprClass:
    case Stmt::ObjCIsaExprClass:
    case Stmt::ObjCProtocolExprClass:
    case Stmt::ObjCSelectorExprClass:
    case Stmt::ObjCStringLiteralClass:
    case Stmt::ParenListExprClass:
    case Stmt::PredefinedExprClass:
    case Stmt::ShuffleVectorExprClass:
    case Stmt::VAArgExprClass:
    case Stmt::CUDAKernelCallExprClass:
    case Stmt::OpaqueValueExprClass:
    case Stmt::AsTypeExprClass:
    case Stmt::AtomicExprClass:
        // Fall through.

    // Cases we intentionally don't evaluate, since they don't need
    // to be explicitly evaluated.
    case Stmt::AddrLabelExprClass:
    case Stmt::IntegerLiteralClass:
    case Stmt::CharacterLiteralClass:
    case Stmt::CXXBoolLiteralExprClass:
    case Stmt::FloatingLiteralClass:
    case Stmt::SizeOfPackExprClass:
    case Stmt::CXXNullPtrLiteralExprClass:
      // No-op. Simply propagate the current state unchanged.
      break;

    case Stmt::ArraySubscriptExprClass:
      Bldr.takeNodes(Pred);
      VisitLvalArraySubscriptExpr(cast<ArraySubscriptExpr>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::AsmStmtClass:
      Bldr.takeNodes(Pred);
      VisitAsmStmt(cast<AsmStmt>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::BlockDeclRefExprClass: {
      Bldr.takeNodes(Pred);
      const BlockDeclRefExpr *BE = cast<BlockDeclRefExpr>(S);
      VisitCommonDeclRefExpr(BE, BE->getDecl(), Pred, Dst);
      Bldr.addNodes(Dst);
      break;
    }

    case Stmt::BlockExprClass:
      Bldr.takeNodes(Pred);
      VisitBlockExpr(cast<BlockExpr>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::BinaryOperatorClass: {
      const BinaryOperator* B = cast<BinaryOperator>(S);
      if (B->isLogicalOp()) {
        Bldr.takeNodes(Pred);
        VisitLogicalExpr(B, Pred, Dst);
        Bldr.addNodes(Dst);
        break;
      }
      else if (B->getOpcode() == BO_Comma) {
        ProgramStateRef state = Pred->getState();
        Bldr.generateNode(B, Pred,
                          state->BindExpr(B, Pred->getLocationContext(),
                                          state->getSVal(B->getRHS(),
                                                  Pred->getLocationContext())));
        break;
      }

      Bldr.takeNodes(Pred);
      
      if (AMgr.shouldEagerlyAssume() &&
          (B->isRelationalOp() || B->isEqualityOp())) {
        ExplodedNodeSet Tmp;
        VisitBinaryOperator(cast<BinaryOperator>(S), Pred, Tmp);
        evalEagerlyAssume(Dst, Tmp, cast<Expr>(S));
      }
      else
        VisitBinaryOperator(cast<BinaryOperator>(S), Pred, Dst);

      Bldr.addNodes(Dst);
      break;
    }

    case Stmt::CallExprClass:
    case Stmt::CXXOperatorCallExprClass:
    case Stmt::CXXMemberCallExprClass: {
      Bldr.takeNodes(Pred);
      VisitCallExpr(cast<CallExpr>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;
    }

    case Stmt::CXXTemporaryObjectExprClass:
    case Stmt::CXXConstructExprClass: {
      const CXXConstructExpr *C = cast<CXXConstructExpr>(S);
      // For block-level CXXConstructExpr, we don't have a destination region.
      // Let VisitCXXConstructExpr() create one.
      Bldr.takeNodes(Pred);
      VisitCXXConstructExpr(C, 0, Pred, Dst);
      Bldr.addNodes(Dst);
      break;
    }

    case Stmt::CXXNewExprClass: {
      Bldr.takeNodes(Pred);
      const CXXNewExpr *NE = cast<CXXNewExpr>(S);
      VisitCXXNewExpr(NE, Pred, Dst);
      Bldr.addNodes(Dst);
      break;
    }

    case Stmt::CXXDeleteExprClass: {
      Bldr.takeNodes(Pred);
      const CXXDeleteExpr *CDE = cast<CXXDeleteExpr>(S);
      VisitCXXDeleteExpr(CDE, Pred, Dst);
      Bldr.addNodes(Dst);
      break;
    }
      // FIXME: ChooseExpr is really a constant.  We need to fix
      //        the CFG do not model them as explicit control-flow.

    case Stmt::ChooseExprClass: { // __builtin_choose_expr
      Bldr.takeNodes(Pred);
      const ChooseExpr *C = cast<ChooseExpr>(S);
      VisitGuardedExpr(C, C->getLHS(), C->getRHS(), Pred, Dst);
      Bldr.addNodes(Dst);
      break;
    }

    case Stmt::CompoundAssignOperatorClass:
      Bldr.takeNodes(Pred);
      VisitBinaryOperator(cast<BinaryOperator>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::CompoundLiteralExprClass:
      Bldr.takeNodes(Pred);
      VisitCompoundLiteralExpr(cast<CompoundLiteralExpr>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::BinaryConditionalOperatorClass:
    case Stmt::ConditionalOperatorClass: { // '?' operator
      Bldr.takeNodes(Pred);
      const AbstractConditionalOperator *C
        = cast<AbstractConditionalOperator>(S);
      VisitGuardedExpr(C, C->getTrueExpr(), C->getFalseExpr(), Pred, Dst);
      Bldr.addNodes(Dst);
      break;
    }

    case Stmt::CXXThisExprClass:
      Bldr.takeNodes(Pred);
      VisitCXXThisExpr(cast<CXXThisExpr>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::DeclRefExprClass: {
      Bldr.takeNodes(Pred);
      const DeclRefExpr *DE = cast<DeclRefExpr>(S);
      VisitCommonDeclRefExpr(DE, DE->getDecl(), Pred, Dst);
      Bldr.addNodes(Dst);
      break;
    }

    case Stmt::DeclStmtClass:
      Bldr.takeNodes(Pred);
      VisitDeclStmt(cast<DeclStmt>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::ImplicitCastExprClass:
    case Stmt::CStyleCastExprClass:
    case Stmt::CXXStaticCastExprClass:
    case Stmt::CXXDynamicCastExprClass:
    case Stmt::CXXReinterpretCastExprClass:
    case Stmt::CXXConstCastExprClass:
    case Stmt::CXXFunctionalCastExprClass: 
    case Stmt::ObjCBridgedCastExprClass: {
      Bldr.takeNodes(Pred);
      const CastExpr *C = cast<CastExpr>(S);
      // Handle the previsit checks.
      ExplodedNodeSet dstPrevisit;
      getCheckerManager().runCheckersForPreStmt(dstPrevisit, Pred, C, *this);
      
      // Handle the expression itself.
      ExplodedNodeSet dstExpr;
      for (ExplodedNodeSet::iterator i = dstPrevisit.begin(),
                                     e = dstPrevisit.end(); i != e ; ++i) { 
        VisitCast(C, C->getSubExpr(), *i, dstExpr);
      }

      // Handle the postvisit checks.
      getCheckerManager().runCheckersForPostStmt(Dst, dstExpr, C, *this);
      Bldr.addNodes(Dst);
      break;
    }

    case Expr::MaterializeTemporaryExprClass: {
      Bldr.takeNodes(Pred);
      const MaterializeTemporaryExpr *Materialize
                                            = cast<MaterializeTemporaryExpr>(S);
      if (!Materialize->getType()->isRecordType())
        CreateCXXTemporaryObject(Materialize, Pred, Dst);
      else
        Visit(Materialize->GetTemporaryExpr(), Pred, Dst);
      Bldr.addNodes(Dst);
      break;
    }
      
    case Stmt::InitListExprClass:
      Bldr.takeNodes(Pred);
      VisitInitListExpr(cast<InitListExpr>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::MemberExprClass:
      Bldr.takeNodes(Pred);
      VisitMemberExpr(cast<MemberExpr>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::ObjCIvarRefExprClass:
      Bldr.takeNodes(Pred);
      VisitLvalObjCIvarRefExpr(cast<ObjCIvarRefExpr>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::ObjCForCollectionStmtClass:
      Bldr.takeNodes(Pred);
      VisitObjCForCollectionStmt(cast<ObjCForCollectionStmt>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::ObjCMessageExprClass:
      Bldr.takeNodes(Pred);
      VisitObjCMessage(cast<ObjCMessageExpr>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::ObjCAtThrowStmtClass: {
      // FIXME: This is not complete.  We basically treat @throw as
      // an abort.
      Bldr.generateNode(S, Pred, Pred->getState());
      break;
    }

    case Stmt::ReturnStmtClass:
      Bldr.takeNodes(Pred);
      VisitReturnStmt(cast<ReturnStmt>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::OffsetOfExprClass:
      Bldr.takeNodes(Pred);
      VisitOffsetOfExpr(cast<OffsetOfExpr>(S), Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::UnaryExprOrTypeTraitExprClass:
      Bldr.takeNodes(Pred);
      VisitUnaryExprOrTypeTraitExpr(cast<UnaryExprOrTypeTraitExpr>(S),
                                    Pred, Dst);
      Bldr.addNodes(Dst);
      break;

    case Stmt::StmtExprClass: {
      const StmtExpr *SE = cast<StmtExpr>(S);

      if (SE->getSubStmt()->body_empty()) {
        // Empty statement expression.
        assert(SE->getType() == getContext().VoidTy
               && "Empty statement expression must have void type.");
        break;
      }

      if (Expr *LastExpr = dyn_cast<Expr>(*SE->getSubStmt()->body_rbegin())) {
        ProgramStateRef state = Pred->getState();
        Bldr.generateNode(SE, Pred,
                          state->BindExpr(SE, Pred->getLocationContext(),
                                          state->getSVal(LastExpr,
                                                  Pred->getLocationContext())));
      }
      break;
    }

    case Stmt::StringLiteralClass: {
      ProgramStateRef state = Pred->getState();
      SVal V = state->getLValue(cast<StringLiteral>(S));
      Bldr.generateNode(S, Pred, state->BindExpr(S, Pred->getLocationContext(),
                                                 V));
      return;
    }

    case Stmt::UnaryOperatorClass: {
      Bldr.takeNodes(Pred);
      const UnaryOperator *U = cast<UnaryOperator>(S);
      if (AMgr.shouldEagerlyAssume() && (U->getOpcode() == UO_LNot)) {
        ExplodedNodeSet Tmp;
        VisitUnaryOperator(U, Pred, Tmp);
        evalEagerlyAssume(Dst, Tmp, U);
      }
      else
        VisitUnaryOperator(U, Pred, Dst);
      Bldr.addNodes(Dst);
      break;
    }

    case Stmt::PseudoObjectExprClass: {
      Bldr.takeNodes(Pred);
      ProgramStateRef state = Pred->getState();
      const PseudoObjectExpr *PE = cast<PseudoObjectExpr>(S);
      if (const Expr *Result = PE->getResultExpr()) { 
        SVal V = state->getSVal(Result, Pred->getLocationContext());
        Bldr.generateNode(S, Pred,
                          state->BindExpr(S, Pred->getLocationContext(), V));
      }
      else
        Bldr.generateNode(S, Pred,
                          state->BindExpr(S, Pred->getLocationContext(),
                                                   UnknownVal()));

      Bldr.addNodes(Dst);
      break;
    }
  }
}

/// Block entrance.  (Update counters).
void ExprEngine::processCFGBlockEntrance(NodeBuilderWithSinks &nodeBuilder) {
  
  // FIXME: Refactor this into a checker.
  ExplodedNode *pred = nodeBuilder.getContext().getPred();
  
  if (nodeBuilder.getContext().getCurrentBlockCount() >= AMgr.getMaxVisit()) {
    static SimpleProgramPointTag tag("ExprEngine : Block count exceeded");
    nodeBuilder.generateNode(pred->getState(), pred, &tag, true);
  }
}

//===----------------------------------------------------------------------===//
// Branch processing.
//===----------------------------------------------------------------------===//

ProgramStateRef ExprEngine::MarkBranch(ProgramStateRef state,
                                           const Stmt *Terminator,
                                           const LocationContext *LCtx,
                                           bool branchTaken) {

  switch (Terminator->getStmtClass()) {
    default:
      return state;

    case Stmt::BinaryOperatorClass: { // '&&' and '||'

      const BinaryOperator* B = cast<BinaryOperator>(Terminator);
      BinaryOperator::Opcode Op = B->getOpcode();

      assert (Op == BO_LAnd || Op == BO_LOr);

      // For &&, if we take the true branch, then the value of the whole
      // expression is that of the RHS expression.
      //
      // For ||, if we take the false branch, then the value of the whole
      // expression is that of the RHS expression.

      const Expr *Ex = (Op == BO_LAnd && branchTaken) ||
                       (Op == BO_LOr && !branchTaken)
                       ? B->getRHS() : B->getLHS();

      return state->BindExpr(B, LCtx, UndefinedVal(Ex));
    }

    case Stmt::BinaryConditionalOperatorClass:
    case Stmt::ConditionalOperatorClass: { // ?:
      const AbstractConditionalOperator* C
        = cast<AbstractConditionalOperator>(Terminator);

      // For ?, if branchTaken == true then the value is either the LHS or
      // the condition itself. (GNU extension).

      const Expr *Ex;

      if (branchTaken)
        Ex = C->getTrueExpr();
      else
        Ex = C->getFalseExpr();

      return state->BindExpr(C, LCtx, UndefinedVal(Ex));
    }

    case Stmt::ChooseExprClass: { // ?:

      const ChooseExpr *C = cast<ChooseExpr>(Terminator);

      const Expr *Ex = branchTaken ? C->getLHS() : C->getRHS();
      return state->BindExpr(C, LCtx, UndefinedVal(Ex));
    }
  }
}

/// RecoverCastedSymbol - A helper function for ProcessBranch that is used
/// to try to recover some path-sensitivity for casts of symbolic
/// integers that promote their values (which are currently not tracked well).
/// This function returns the SVal bound to Condition->IgnoreCasts if all the
//  cast(s) did was sign-extend the original value.
static SVal RecoverCastedSymbol(ProgramStateManager& StateMgr,
                                ProgramStateRef state,
                                const Stmt *Condition,
                                const LocationContext *LCtx,
                                ASTContext &Ctx) {

  const Expr *Ex = dyn_cast<Expr>(Condition);
  if (!Ex)
    return UnknownVal();

  uint64_t bits = 0;
  bool bitsInit = false;

  while (const CastExpr *CE = dyn_cast<CastExpr>(Ex)) {
    QualType T = CE->getType();

    if (!T->isIntegerType())
      return UnknownVal();

    uint64_t newBits = Ctx.getTypeSize(T);
    if (!bitsInit || newBits < bits) {
      bitsInit = true;
      bits = newBits;
    }

    Ex = CE->getSubExpr();
  }

  // We reached a non-cast.  Is it a symbolic value?
  QualType T = Ex->getType();

  if (!bitsInit || !T->isIntegerType() || Ctx.getTypeSize(T) > bits)
    return UnknownVal();

  return state->getSVal(Ex, LCtx);
}

void ExprEngine::processBranch(const Stmt *Condition, const Stmt *Term,
                               NodeBuilderContext& BldCtx,
                               ExplodedNode *Pred,
                               ExplodedNodeSet &Dst,
                               const CFGBlock *DstT,
                               const CFGBlock *DstF) {
  currentBuilderContext = &BldCtx;

  // Check for NULL conditions; e.g. "for(;;)"
  if (!Condition) {
    BranchNodeBuilder NullCondBldr(Pred, Dst, BldCtx, DstT, DstF);
    NullCondBldr.markInfeasible(false);
    NullCondBldr.generateNode(Pred->getState(), true, Pred);
    return;
  }

  PrettyStackTraceLoc CrashInfo(getContext().getSourceManager(),
                                Condition->getLocStart(),
                                "Error evaluating branch");

  ExplodedNodeSet CheckersOutSet;
  getCheckerManager().runCheckersForBranchCondition(Condition, CheckersOutSet,
                                                    Pred, *this);
  // We generated only sinks.
  if (CheckersOutSet.empty())
    return;

  BranchNodeBuilder builder(CheckersOutSet, Dst, BldCtx, DstT, DstF);
  for (NodeBuilder::iterator I = CheckersOutSet.begin(),
                             E = CheckersOutSet.end(); E != I; ++I) {
    ExplodedNode *PredI = *I;

    if (PredI->isSink())
      continue;

    ProgramStateRef PrevState = Pred->getState();
    SVal X = PrevState->getSVal(Condition, Pred->getLocationContext());

    if (X.isUnknownOrUndef()) {
      // Give it a chance to recover from unknown.
      if (const Expr *Ex = dyn_cast<Expr>(Condition)) {
        if (Ex->getType()->isIntegerType()) {
          // Try to recover some path-sensitivity.  Right now casts of symbolic
          // integers that promote their values are currently not tracked well.
          // If 'Condition' is such an expression, try and recover the
          // underlying value and use that instead.
          SVal recovered = RecoverCastedSymbol(getStateManager(),
                                               PrevState, Condition,
                                               Pred->getLocationContext(),
                                               getContext());

          if (!recovered.isUnknown()) {
            X = recovered;
          }
        }
      }
    }
    
    const LocationContext *LCtx = PredI->getLocationContext();

    // If the condition is still unknown, give up.
    if (X.isUnknownOrUndef()) {
      builder.generateNode(MarkBranch(PrevState, Term, LCtx, true),
                           true, PredI);
      builder.generateNode(MarkBranch(PrevState, Term, LCtx, false),
                           false, PredI);
      continue;
    }

    DefinedSVal V = cast<DefinedSVal>(X);

    // Process the true branch.
    if (builder.isFeasible(true)) {
      if (ProgramStateRef state = PrevState->assume(V, true))
        builder.generateNode(MarkBranch(state, Term, LCtx, true),
                             true, PredI);
      else
        builder.markInfeasible(true);
    }

    // Process the false branch.
    if (builder.isFeasible(false)) {
      if (ProgramStateRef state = PrevState->assume(V, false))
        builder.generateNode(MarkBranch(state, Term, LCtx, false),
                             false, PredI);
      else
        builder.markInfeasible(false);
    }
  }
  currentBuilderContext = 0;
}

/// processIndirectGoto - Called by CoreEngine.  Used to generate successor
///  nodes by processing the 'effects' of a computed goto jump.
void ExprEngine::processIndirectGoto(IndirectGotoNodeBuilder &builder) {

  ProgramStateRef state = builder.getState();
  SVal V = state->getSVal(builder.getTarget(), builder.getLocationContext());

  // Three possibilities:
  //
  //   (1) We know the computed label.
  //   (2) The label is NULL (or some other constant), or Undefined.
  //   (3) We have no clue about the label.  Dispatch to all targets.
  //

  typedef IndirectGotoNodeBuilder::iterator iterator;

  if (isa<loc::GotoLabel>(V)) {
    const LabelDecl *L = cast<loc::GotoLabel>(V).getLabel();

    for (iterator I = builder.begin(), E = builder.end(); I != E; ++I) {
      if (I.getLabel() == L) {
        builder.generateNode(I, state);
        return;
      }
    }

    llvm_unreachable("No block with label.");
  }

  if (isa<loc::ConcreteInt>(V) || isa<UndefinedVal>(V)) {
    // Dispatch to the first target and mark it as a sink.
    //ExplodedNode* N = builder.generateNode(builder.begin(), state, true);
    // FIXME: add checker visit.
    //    UndefBranches.insert(N);
    return;
  }

  // This is really a catch-all.  We don't support symbolics yet.
  // FIXME: Implement dispatch for symbolic pointers.

  for (iterator I=builder.begin(), E=builder.end(); I != E; ++I)
    builder.generateNode(I, state);
}

/// ProcessEndPath - Called by CoreEngine.  Used to generate end-of-path
///  nodes when the control reaches the end of a function.
void ExprEngine::processEndOfFunction(NodeBuilderContext& BC) {
  StateMgr.EndPath(BC.Pred->getState());
  ExplodedNodeSet Dst;
  getCheckerManager().runCheckersForEndPath(BC, Dst, *this);
  Engine.enqueueEndOfFunction(Dst);
}

/// ProcessSwitch - Called by CoreEngine.  Used to generate successor
///  nodes by processing the 'effects' of a switch statement.
void ExprEngine::processSwitch(SwitchNodeBuilder& builder) {
  typedef SwitchNodeBuilder::iterator iterator;
  ProgramStateRef state = builder.getState();
  const Expr *CondE = builder.getCondition();
  SVal  CondV_untested = state->getSVal(CondE, builder.getLocationContext());

  if (CondV_untested.isUndef()) {
    //ExplodedNode* N = builder.generateDefaultCaseNode(state, true);
    // FIXME: add checker
    //UndefBranches.insert(N);

    return;
  }
  DefinedOrUnknownSVal CondV = cast<DefinedOrUnknownSVal>(CondV_untested);

  ProgramStateRef DefaultSt = state;
  
  iterator I = builder.begin(), EI = builder.end();
  bool defaultIsFeasible = I == EI;

  for ( ; I != EI; ++I) {
    // Successor may be pruned out during CFG construction.
    if (!I.getBlock())
      continue;
    
    const CaseStmt *Case = I.getCase();

    // Evaluate the LHS of the case value.
    llvm::APSInt V1 = Case->getLHS()->EvaluateKnownConstInt(getContext());
    assert(V1.getBitWidth() == getContext().getTypeSize(CondE->getType()));

    // Get the RHS of the case, if it exists.
    llvm::APSInt V2;
    if (const Expr *E = Case->getRHS())
      V2 = E->EvaluateKnownConstInt(getContext());
    else
      V2 = V1;

    // FIXME: Eventually we should replace the logic below with a range
    //  comparison, rather than concretize the values within the range.
    //  This should be easy once we have "ranges" for NonLVals.

    do {
      nonloc::ConcreteInt CaseVal(getBasicVals().getValue(V1));
      DefinedOrUnknownSVal Res = svalBuilder.evalEQ(DefaultSt ? DefaultSt : state,
                                               CondV, CaseVal);

      // Now "assume" that the case matches.
      if (ProgramStateRef stateNew = state->assume(Res, true)) {
        builder.generateCaseStmtNode(I, stateNew);

        // If CondV evaluates to a constant, then we know that this
        // is the *only* case that we can take, so stop evaluating the
        // others.
        if (isa<nonloc::ConcreteInt>(CondV))
          return;
      }

      // Now "assume" that the case doesn't match.  Add this state
      // to the default state (if it is feasible).
      if (DefaultSt) {
        if (ProgramStateRef stateNew = DefaultSt->assume(Res, false)) {
          defaultIsFeasible = true;
          DefaultSt = stateNew;
        }
        else {
          defaultIsFeasible = false;
          DefaultSt = NULL;
        }
      }

      // Concretize the next value in the range.
      if (V1 == V2)
        break;

      ++V1;
      assert (V1 <= V2);

    } while (true);
  }

  if (!defaultIsFeasible)
    return;

  // If we have switch(enum value), the default branch is not
  // feasible if all of the enum constants not covered by 'case:' statements
  // are not feasible values for the switch condition.
  //
  // Note that this isn't as accurate as it could be.  Even if there isn't
  // a case for a particular enum value as long as that enum value isn't
  // feasible then it shouldn't be considered for making 'default:' reachable.
  const SwitchStmt *SS = builder.getSwitch();
  const Expr *CondExpr = SS->getCond()->IgnoreParenImpCasts();
  if (CondExpr->getType()->getAs<EnumType>()) {
    if (SS->isAllEnumCasesCovered())
      return;
  }

  builder.generateDefaultCaseNode(DefaultSt);
}

//===----------------------------------------------------------------------===//
// Transfer functions: Loads and stores.
//===----------------------------------------------------------------------===//

void ExprEngine::VisitCommonDeclRefExpr(const Expr *Ex, const NamedDecl *D,
                                        ExplodedNode *Pred,
                                        ExplodedNodeSet &Dst) {
  StmtNodeBuilder Bldr(Pred, Dst, *currentBuilderContext);

  ProgramStateRef state = Pred->getState();
  const LocationContext *LCtx = Pred->getLocationContext();

  if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
    assert(Ex->isLValue());
    SVal V = state->getLValue(VD, Pred->getLocationContext());

    // For references, the 'lvalue' is the pointer address stored in the
    // reference region.
    if (VD->getType()->isReferenceType()) {
      if (const MemRegion *R = V.getAsRegion())
        V = state->getSVal(R);
      else
        V = UnknownVal();
    }

    Bldr.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, V), false, 0,
                      ProgramPoint::PostLValueKind);
    return;
  }
  if (const EnumConstantDecl *ED = dyn_cast<EnumConstantDecl>(D)) {
    assert(!Ex->isLValue());
    SVal V = svalBuilder.makeIntVal(ED->getInitVal());
    Bldr.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, V));
    return;
  }
  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
    SVal V = svalBuilder.getFunctionPointer(FD);
    Bldr.generateNode(Ex, Pred, state->BindExpr(Ex, LCtx, V), false, 0,
                      ProgramPoint::PostLValueKind);
    return;
  }
  assert (false &&
          "ValueDecl support for this ValueDecl not implemented.");
}

/// VisitArraySubscriptExpr - Transfer function for array accesses
void ExprEngine::VisitLvalArraySubscriptExpr(const ArraySubscriptExpr *A,
                                             ExplodedNode *Pred,
                                             ExplodedNodeSet &Dst){

  const Expr *Base = A->getBase()->IgnoreParens();
  const Expr *Idx  = A->getIdx()->IgnoreParens();
  

  ExplodedNodeSet checkerPreStmt;
  getCheckerManager().runCheckersForPreStmt(checkerPreStmt, Pred, A, *this);

  StmtNodeBuilder Bldr(checkerPreStmt, Dst, *currentBuilderContext);

  for (ExplodedNodeSet::iterator it = checkerPreStmt.begin(),
                                 ei = checkerPreStmt.end(); it != ei; ++it) {
    const LocationContext *LCtx = (*it)->getLocationContext();
    ProgramStateRef state = (*it)->getState();
    SVal V = state->getLValue(A->getType(),
                              state->getSVal(Idx, LCtx),
                              state->getSVal(Base, LCtx));
    assert(A->isLValue());
    Bldr.generateNode(A, *it, state->BindExpr(A, LCtx, V),
                      false, 0, ProgramPoint::PostLValueKind);
  }
}

/// VisitMemberExpr - Transfer function for member expressions.
void ExprEngine::VisitMemberExpr(const MemberExpr *M, ExplodedNode *Pred,
                                 ExplodedNodeSet &TopDst) {

  StmtNodeBuilder Bldr(Pred, TopDst, *currentBuilderContext);
  ExplodedNodeSet Dst;
  Decl *member = M->getMemberDecl();
  if (VarDecl *VD = dyn_cast<VarDecl>(member)) {
    assert(M->isLValue());
    Bldr.takeNodes(Pred);
    VisitCommonDeclRefExpr(M, VD, Pred, Dst);
    Bldr.addNodes(Dst);
    return;
  }
  
  FieldDecl *field = dyn_cast<FieldDecl>(member);
  if (!field) // FIXME: skipping member expressions for non-fields
    return;

  Expr *baseExpr = M->getBase()->IgnoreParens();
  ProgramStateRef state = Pred->getState();
  const LocationContext *LCtx = Pred->getLocationContext();
  SVal baseExprVal = state->getSVal(baseExpr, Pred->getLocationContext());
  if (isa<nonloc::LazyCompoundVal>(baseExprVal) ||
      isa<nonloc::CompoundVal>(baseExprVal) ||
      // FIXME: This can originate by conjuring a symbol for an unknown
      // temporary struct object, see test/Analysis/fields.c:
      // (p = getit()).x
      isa<nonloc::SymbolVal>(baseExprVal)) {
    Bldr.generateNode(M, Pred, state->BindExpr(M, LCtx, UnknownVal()));
    return;
  }

  // FIXME: Should we insert some assumption logic in here to determine
  // if "Base" is a valid piece of memory?  Before we put this assumption
  // later when using FieldOffset lvals (which we no longer have).

  // For all other cases, compute an lvalue.    
  SVal L = state->getLValue(field, baseExprVal);
  if (M->isLValue())
    Bldr.generateNode(M, Pred, state->BindExpr(M, LCtx, L), false, 0,
                      ProgramPoint::PostLValueKind);
  else {
    Bldr.takeNodes(Pred);
    evalLoad(Dst, M, Pred, state, L);
    Bldr.addNodes(Dst);
  }
}

/// evalBind - Handle the semantics of binding a value to a specific location.
///  This method is used by evalStore and (soon) VisitDeclStmt, and others.
void ExprEngine::evalBind(ExplodedNodeSet &Dst, const Stmt *StoreE,
                          ExplodedNode *Pred,
                          SVal location, SVal Val, bool atDeclInit,
                          ProgramPoint::Kind PointKind) {

  // Do a previsit of the bind.
  ExplodedNodeSet CheckedSet;
  getCheckerManager().runCheckersForBind(CheckedSet, Pred, location, Val,
                                         StoreE, *this, PointKind);

  // TODO:AZ Remove TmpDst after NB refactoring is done.
  ExplodedNodeSet TmpDst;
  StmtNodeBuilder Bldr(CheckedSet, TmpDst, *currentBuilderContext);

  for (ExplodedNodeSet::iterator I = CheckedSet.begin(), E = CheckedSet.end();
       I!=E; ++I) {
    ProgramStateRef state = (*I)->getState();

    if (atDeclInit) {
      const VarRegion *VR =
        cast<VarRegion>(cast<loc::MemRegionVal>(location).getRegion());

      state = state->bindDecl(VR, Val);
    } else {
      state = state->bindLoc(location, Val);
    }

    Bldr.generateNode(StoreE, *I, state, false, 0, PointKind);
  }

  Dst.insert(TmpDst);
}

/// evalStore - Handle the semantics of a store via an assignment.
///  @param Dst The node set to store generated state nodes
///  @param AssignE The assignment expression if the store happens in an 
///         assignment.
///  @param LocatioinE The location expression that is stored to.
///  @param state The current simulation state
///  @param location The location to store the value
///  @param Val The value to be stored
void ExprEngine::evalStore(ExplodedNodeSet &Dst, const Expr *AssignE,
                             const Expr *LocationE,
                             ExplodedNode *Pred,
                             ProgramStateRef state, SVal location, SVal Val,
                             const ProgramPointTag *tag) {
  // Proceed with the store.  We use AssignE as the anchor for the PostStore
  // ProgramPoint if it is non-NULL, and LocationE otherwise.
  const Expr *StoreE = AssignE ? AssignE : LocationE;

  if (isa<loc::ObjCPropRef>(location)) {
    loc::ObjCPropRef prop = cast<loc::ObjCPropRef>(location);
    return VisitObjCMessage(ObjCPropertySetter(prop.getPropRefExpr(),
                                               StoreE, Val), Pred, Dst);
  }

  // Evaluate the location (checks for bad dereferences).
  ExplodedNodeSet Tmp;
  evalLocation(Tmp, LocationE, Pred, state, location, tag, false);

  if (Tmp.empty())
    return;

  if (location.isUndef())
    return;

  for (ExplodedNodeSet::iterator NI=Tmp.begin(), NE=Tmp.end(); NI!=NE; ++NI)
    evalBind(Dst, StoreE, *NI, location, Val, false,
             ProgramPoint::PostStoreKind);
}

void ExprEngine::evalLoad(ExplodedNodeSet &Dst, const Expr *Ex,
                            ExplodedNode *Pred,
                            ProgramStateRef state, SVal location,
                            const ProgramPointTag *tag, QualType LoadTy) {
  assert(!isa<NonLoc>(location) && "location cannot be a NonLoc.");

  if (isa<loc::ObjCPropRef>(location)) {
    loc::ObjCPropRef prop = cast<loc::ObjCPropRef>(location);
    return VisitObjCMessage(ObjCPropertyGetter(prop.getPropRefExpr(), Ex),
                            Pred, Dst);
  }

  // Are we loading from a region?  This actually results in two loads; one
  // to fetch the address of the referenced value and one to fetch the
  // referenced value.
  if (const TypedValueRegion *TR =
        dyn_cast_or_null<TypedValueRegion>(location.getAsRegion())) {

    QualType ValTy = TR->getValueType();
    if (const ReferenceType *RT = ValTy->getAs<ReferenceType>()) {
      static SimpleProgramPointTag
             loadReferenceTag("ExprEngine : Load Reference");
      ExplodedNodeSet Tmp;
      evalLoadCommon(Tmp, Ex, Pred, state, location, &loadReferenceTag,
                     getContext().getPointerType(RT->getPointeeType()));

      // Perform the load from the referenced value.
      for (ExplodedNodeSet::iterator I=Tmp.begin(), E=Tmp.end() ; I!=E; ++I) {
        state = (*I)->getState();
        location = state->getSVal(Ex, (*I)->getLocationContext());
        evalLoadCommon(Dst, Ex, *I, state, location, tag, LoadTy);
      }
      return;
    }
  }

  evalLoadCommon(Dst, Ex, Pred, state, location, tag, LoadTy);
}

void ExprEngine::evalLoadCommon(ExplodedNodeSet &Dst, const Expr *Ex,
                                  ExplodedNode *Pred,
                                  ProgramStateRef state, SVal location,
                                  const ProgramPointTag *tag, QualType LoadTy) {

  // Evaluate the location (checks for bad dereferences).
  ExplodedNodeSet Tmp;
  evalLocation(Tmp, Ex, Pred, state, location, tag, true);
  if (Tmp.empty())
    return;

  StmtNodeBuilder Bldr(Tmp, Dst, *currentBuilderContext);
  if (location.isUndef())
    return;

  // Proceed with the load.
  for (ExplodedNodeSet::iterator NI=Tmp.begin(), NE=Tmp.end(); NI!=NE; ++NI) {
    state = (*NI)->getState();
    const LocationContext *LCtx = (*NI)->getLocationContext();

    if (location.isUnknown()) {
      // This is important.  We must nuke the old binding.
      Bldr.generateNode(Ex, *NI, state->BindExpr(Ex, LCtx, UnknownVal()),
                        false, tag, ProgramPoint::PostLoadKind);
    }
    else {
      if (LoadTy.isNull())
        LoadTy = Ex->getType();
      SVal V = state->getSVal(cast<Loc>(location), LoadTy);
      Bldr.generateNode(Ex, *NI, state->bindExprAndLocation(Ex, LCtx,
                                                            location, V),
                        false, tag, ProgramPoint::PostLoadKind);
    }
  }
}

void ExprEngine::evalLocation(ExplodedNodeSet &Dst, const Stmt *S,
                                ExplodedNode *Pred,
                                ProgramStateRef state, SVal location,
                                const ProgramPointTag *tag, bool isLoad) {
  StmtNodeBuilder BldrTop(Pred, Dst, *currentBuilderContext);
  // Early checks for performance reason.
  if (location.isUnknown()) {
    return;
  }

  ExplodedNodeSet Src;
  BldrTop.takeNodes(Pred);
  StmtNodeBuilder Bldr(Pred, Src, *currentBuilderContext);
  if (Pred->getState() != state) {
    // Associate this new state with an ExplodedNode.
    // FIXME: If I pass null tag, the graph is incorrect, e.g for
    //   int *p;
    //   p = 0;
    //   *p = 0xDEADBEEF;
    // "p = 0" is not noted as "Null pointer value stored to 'p'" but
    // instead "int *p" is noted as
    // "Variable 'p' initialized to a null pointer value"
    
    // FIXME: why is 'tag' not used instead of etag?
    static SimpleProgramPointTag etag("ExprEngine: Location");

    Bldr.generateNode(S, Pred, state, false, &etag);
  }
  ExplodedNodeSet Tmp;
  getCheckerManager().runCheckersForLocation(Tmp, Src, location, isLoad, S,
                                             *this);
  BldrTop.addNodes(Tmp);
}

std::pair<const ProgramPointTag *, const ProgramPointTag*>
ExprEngine::getEagerlyAssumeTags() {
  static SimpleProgramPointTag
         EagerlyAssumeTrue("ExprEngine : Eagerly Assume True"),
         EagerlyAssumeFalse("ExprEngine : Eagerly Assume False");
  return std::make_pair(&EagerlyAssumeTrue, &EagerlyAssumeFalse);
}

void ExprEngine::evalEagerlyAssume(ExplodedNodeSet &Dst, ExplodedNodeSet &Src,
                                   const Expr *Ex) {
  StmtNodeBuilder Bldr(Src, Dst, *currentBuilderContext);
  
  for (ExplodedNodeSet::iterator I=Src.begin(), E=Src.end(); I!=E; ++I) {
    ExplodedNode *Pred = *I;
    // Test if the previous node was as the same expression.  This can happen
    // when the expression fails to evaluate to anything meaningful and
    // (as an optimization) we don't generate a node.
    ProgramPoint P = Pred->getLocation();
    if (!isa<PostStmt>(P) || cast<PostStmt>(P).getStmt() != Ex) {
      continue;
    }

    ProgramStateRef state = Pred->getState();
    SVal V = state->getSVal(Ex, Pred->getLocationContext());
    nonloc::SymbolVal *SEV = dyn_cast<nonloc::SymbolVal>(&V);
    if (SEV && SEV->isExpression()) {
      const std::pair<const ProgramPointTag *, const ProgramPointTag*> &tags =
        getEagerlyAssumeTags();

      // First assume that the condition is true.
      if (ProgramStateRef StateTrue = state->assume(*SEV, true)) {
        SVal Val = svalBuilder.makeIntVal(1U, Ex->getType());        
        StateTrue = StateTrue->BindExpr(Ex, Pred->getLocationContext(), Val);
        Bldr.generateNode(Ex, Pred, StateTrue, false, tags.first);
      }

      // Next, assume that the condition is false.
      if (ProgramStateRef StateFalse = state->assume(*SEV, false)) {
        SVal Val = svalBuilder.makeIntVal(0U, Ex->getType());
        StateFalse = StateFalse->BindExpr(Ex, Pred->getLocationContext(), Val);
        Bldr.generateNode(Ex, Pred, StateFalse, false, tags.second);
      }
    }
  }
}

void ExprEngine::VisitAsmStmt(const AsmStmt *A, ExplodedNode *Pred,
                                ExplodedNodeSet &Dst) {
  VisitAsmStmtHelperOutputs(A, A->begin_outputs(), A->end_outputs(), Pred, Dst);
}

void ExprEngine::VisitAsmStmtHelperOutputs(const AsmStmt *A,
                                             AsmStmt::const_outputs_iterator I,
                                             AsmStmt::const_outputs_iterator E,
                                     ExplodedNode *Pred, ExplodedNodeSet &Dst) {
  if (I == E) {
    VisitAsmStmtHelperInputs(A, A->begin_inputs(), A->end_inputs(), Pred, Dst);
    return;
  }

  ExplodedNodeSet Tmp;
  Visit(*I, Pred, Tmp);
  ++I;

  for (ExplodedNodeSet::iterator NI = Tmp.begin(), NE = Tmp.end();NI != NE;++NI)
    VisitAsmStmtHelperOutputs(A, I, E, *NI, Dst);
}

void ExprEngine::VisitAsmStmtHelperInputs(const AsmStmt *A,
                                            AsmStmt::const_inputs_iterator I,
                                            AsmStmt::const_inputs_iterator E,
                                            ExplodedNode *Pred,
                                            ExplodedNodeSet &Dst) {
  if (I == E) {
    StmtNodeBuilder Bldr(Pred, Dst, *currentBuilderContext);
    // We have processed both the inputs and the outputs.  All of the outputs
    // should evaluate to Locs.  Nuke all of their values.

    // FIXME: Some day in the future it would be nice to allow a "plug-in"
    // which interprets the inline asm and stores proper results in the
    // outputs.

    ProgramStateRef state = Pred->getState();

    for (AsmStmt::const_outputs_iterator OI = A->begin_outputs(),
                                   OE = A->end_outputs(); OI != OE; ++OI) {

      SVal X = state->getSVal(*OI, Pred->getLocationContext());
      assert (!isa<NonLoc>(X));  // Should be an Lval, or unknown, undef.

      if (isa<Loc>(X))
        state = state->bindLoc(cast<Loc>(X), UnknownVal());
    }

    Bldr.generateNode(A, Pred, state);
    return;
  }

  ExplodedNodeSet Tmp;
  Visit(*I, Pred, Tmp);

  ++I;

  for (ExplodedNodeSet::iterator NI = Tmp.begin(), NE = Tmp.end(); NI!=NE; ++NI)
    VisitAsmStmtHelperInputs(A, I, E, *NI, Dst);
}


//===----------------------------------------------------------------------===//
// Visualization.
//===----------------------------------------------------------------------===//

#ifndef NDEBUG
static ExprEngine* GraphPrintCheckerState;
static SourceManager* GraphPrintSourceManager;

namespace llvm {
template<>
struct DOTGraphTraits<ExplodedNode*> :
  public DefaultDOTGraphTraits {

  DOTGraphTraits (bool isSimple=false) : DefaultDOTGraphTraits(isSimple) {}

  // FIXME: Since we do not cache error nodes in ExprEngine now, this does not
  // work.
  static std::string getNodeAttributes(const ExplodedNode *N, void*) {

#if 0
      // FIXME: Replace with a general scheme to tell if the node is
      // an error node.
    if (GraphPrintCheckerState->isImplicitNullDeref(N) ||
        GraphPrintCheckerState->isExplicitNullDeref(N) ||
        GraphPrintCheckerState->isUndefDeref(N) ||
        GraphPrintCheckerState->isUndefStore(N) ||
        GraphPrintCheckerState->isUndefControlFlow(N) ||
        GraphPrintCheckerState->isUndefResult(N) ||
        GraphPrintCheckerState->isBadCall(N) ||
        GraphPrintCheckerState->isUndefArg(N))
      return "color=\"red\",style=\"filled\"";

    if (GraphPrintCheckerState->isNoReturnCall(N))
      return "color=\"blue\",style=\"filled\"";
#endif
    return "";
  }

  static std::string getNodeLabel(const ExplodedNode *N, void*){

    std::string sbuf;
    llvm::raw_string_ostream Out(sbuf);

    // 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::CallEnterKind:
        Out << "CallEnter";
        break;

      case ProgramPoint::CallExitKind:
        Out << "CallExit";
        break;

      default: {
        if (StmtPoint *L = dyn_cast<StmtPoint>(&Loc)) {
          const Stmt *S = L->getStmt();
          SourceLocation SLoc = S->getLocStart();

          Out << S->getStmtClassName() << ' ' << (void*) S << ' ';
          LangOptions LO; // FIXME.
          S->printPretty(Out, 0, PrintingPolicy(LO));

          if (SLoc.isFileID()) {
            Out << "\\lline="
              << GraphPrintSourceManager->getExpansionLineNumber(SLoc)
              << " col="
              << GraphPrintSourceManager->getExpansionColumnNumber(SLoc)
              << "\\l";
          }

          if (isa<PreStmt>(Loc))
            Out << "\\lPreStmt\\l;";
          else if (isa<PostLoad>(Loc))
            Out << "\\lPostLoad\\l;";
          else if (isa<PostStore>(Loc))
            Out << "\\lPostStore\\l";
          else if (isa<PostLValue>(Loc))
            Out << "\\lPostLValue\\l";

#if 0
            // FIXME: Replace with a general scheme to determine
            // the name of the check.
          if (GraphPrintCheckerState->isImplicitNullDeref(N))
            Out << "\\|Implicit-Null Dereference.\\l";
          else if (GraphPrintCheckerState->isExplicitNullDeref(N))
            Out << "\\|Explicit-Null Dereference.\\l";
          else if (GraphPrintCheckerState->isUndefDeref(N))
            Out << "\\|Dereference of undefialied value.\\l";
          else if (GraphPrintCheckerState->isUndefStore(N))
            Out << "\\|Store to Undefined Loc.";
          else if (GraphPrintCheckerState->isUndefResult(N))
            Out << "\\|Result of operation is undefined.";
          else if (GraphPrintCheckerState->isNoReturnCall(N))
            Out << "\\|Call to function marked \"noreturn\".";
          else if (GraphPrintCheckerState->isBadCall(N))
            Out << "\\|Call to NULL/Undefined.";
          else if (GraphPrintCheckerState->isUndefArg(N))
            Out << "\\|Argument in call is undefined";
#endif

          break;
        }

        const BlockEdge &E = cast<BlockEdge>(Loc);
        Out << "Edge: (B" << E.getSrc()->getBlockID() << ", B"
            << E.getDst()->getBlockID()  << ')';

        if (const Stmt *T = E.getSrc()->getTerminator()) {

          SourceLocation SLoc = T->getLocStart();

          Out << "\\|Terminator: ";
          LangOptions LO; // FIXME.
          E.getSrc()->printTerminator(Out, LO);

          if (SLoc.isFileID()) {
            Out << "\\lline="
              << GraphPrintSourceManager->getExpansionLineNumber(SLoc)
              << " col="
              << GraphPrintSourceManager->getExpansionColumnNumber(SLoc);
          }

          if (isa<SwitchStmt>(T)) {
            const Stmt *Label = E.getDst()->getLabel();

            if (Label) {
              if (const CaseStmt *C = dyn_cast<CaseStmt>(Label)) {
                Out << "\\lcase ";
                LangOptions LO; // FIXME.
                C->getLHS()->printPretty(Out, 0, PrintingPolicy(LO));

                if (const Stmt *RHS = C->getRHS()) {
                  Out << " .. ";
                  RHS->printPretty(Out, 0, PrintingPolicy(LO));
                }

                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 0
          // FIXME: Replace with a general scheme to determine
          // the name of the check.
        if (GraphPrintCheckerState->isUndefControlFlow(N)) {
          Out << "\\|Control-flow based on\\lUndefined value.\\l";
        }
#endif
      }
    }

    ProgramStateRef state = N->getState();
    Out << "\\|StateID: " << (void*) state.getPtr()
        << " NodeID: " << (void*) N << "\\|";
    state->printDOT(Out);

    Out << "\\l";    

    if (const ProgramPointTag *tag = Loc.getTag()) {
      Out << "\\|Tag: " << tag->getTagDescription(); 
      Out << "\\l";
    }
    return Out.str();
  }
};
} // end llvm namespace
#endif

#ifndef NDEBUG
template <typename ITERATOR>
ExplodedNode *GetGraphNode(ITERATOR I) { return *I; }

template <> ExplodedNode*
GetGraphNode<llvm::DenseMap<ExplodedNode*, Expr*>::iterator>
  (llvm::DenseMap<ExplodedNode*, Expr*>::iterator I) {
  return I->first;
}
#endif

void ExprEngine::ViewGraph(bool trim) {
#ifndef NDEBUG
  if (trim) {
    std::vector<ExplodedNode*> Src;

    // Flush any outstanding reports to make sure we cover all the nodes.
    // This does not cause them to get displayed.
    for (BugReporter::iterator I=BR.begin(), E=BR.end(); I!=E; ++I)
      const_cast<BugType*>(*I)->FlushReports(BR);

    // Iterate through the reports and get their nodes.
    for (BugReporter::EQClasses_iterator
           EI = BR.EQClasses_begin(), EE = BR.EQClasses_end(); EI != EE; ++EI) {
      BugReportEquivClass& EQ = *EI;
      const BugReport &R = **EQ.begin();
      ExplodedNode *N = const_cast<ExplodedNode*>(R.getErrorNode());
      if (N) Src.push_back(N);
    }

    ViewGraph(&Src[0], &Src[0]+Src.size());
  }
  else {
    GraphPrintCheckerState = this;
    GraphPrintSourceManager = &getContext().getSourceManager();

    llvm::ViewGraph(*G.roots_begin(), "ExprEngine");

    GraphPrintCheckerState = NULL;
    GraphPrintSourceManager = NULL;
  }
#endif
}

void ExprEngine::ViewGraph(ExplodedNode** Beg, ExplodedNode** End) {
#ifndef NDEBUG
  GraphPrintCheckerState = this;
  GraphPrintSourceManager = &getContext().getSourceManager();

  std::auto_ptr<ExplodedGraph> TrimmedG(G.Trim(Beg, End).first);

  if (!TrimmedG.get())
    llvm::errs() << "warning: Trimmed ExplodedGraph is empty.\n";
  else
    llvm::ViewGraph(*TrimmedG->roots_begin(), "TrimmedExprEngine");

  GraphPrintCheckerState = NULL;
  GraphPrintSourceManager = NULL;
#endif
}