CoreEngine.cpp revision dd7ddf2b2296f95e7591ca3f9791f0eb9a15ee42 
1//==- CoreEngine.cpp - Path-Sensitive Dataflow Engine ------------*- C++ -*-//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10//  This file defines a generic engine for intraprocedural, path-sensitive,
11//  dataflow analysis via graph reachability engine.
12//
13//===----------------------------------------------------------------------===//
14
15#include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
16#include "clang/StaticAnalyzer/Core/PathSensitive/CoreEngine.h"
17#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
18#include "clang/Index/TranslationUnit.h"
19#include "clang/AST/Expr.h"
20#include "clang/AST/StmtCXX.h"
21#include "llvm/Support/Casting.h"
22#include "llvm/ADT/DenseMap.h"
23using namespace clang;
24using namespace ento;
25
26//===----------------------------------------------------------------------===//
27// Worklist classes for exploration of reachable states.
28//===----------------------------------------------------------------------===//
29
30WorkList::Visitor::~Visitor() {}
31
32namespace {
33class DFS : public WorkList {
34  SmallVector<WorkListUnit,20> Stack;
35public:
36  virtual bool hasWork() const {
37    return !Stack.empty();
38  }
39
40  virtual void enqueue(const WorkListUnit& U) {
41    Stack.push_back(U);
42  }
43
44  virtual WorkListUnit dequeue() {
45    assert (!Stack.empty());
46    const WorkListUnit& U = Stack.back();
47    Stack.pop_back(); // This technically "invalidates" U, but we are fine.
48    return U;
49  }
50
51  virtual bool visitItemsInWorkList(Visitor &V) {
52    for (SmallVectorImpl<WorkListUnit>::iterator
53         I = Stack.begin(), E = Stack.end(); I != E; ++I) {
54      if (V.visit(*I))
55        return true;
56    }
57    return false;
58  }
59};
60
61class BFS : public WorkList {
62  std::deque<WorkListUnit> Queue;
63public:
64  virtual bool hasWork() const {
65    return !Queue.empty();
66  }
67
68  virtual void enqueue(const WorkListUnit& U) {
69    Queue.push_front(U);
70  }
71
72  virtual WorkListUnit dequeue() {
73    WorkListUnit U = Queue.front();
74    Queue.pop_front();
75    return U;
76  }
77
78  virtual bool visitItemsInWorkList(Visitor &V) {
79    for (std::deque<WorkListUnit>::iterator
80         I = Queue.begin(), E = Queue.end(); I != E; ++I) {
81      if (V.visit(*I))
82        return true;
83    }
84    return false;
85  }
86};
87
88} // end anonymous namespace
89
90// Place the dstor for WorkList here because it contains virtual member
91// functions, and we the code for the dstor generated in one compilation unit.
92WorkList::~WorkList() {}
93
94WorkList *WorkList::makeDFS() { return new DFS(); }
95WorkList *WorkList::makeBFS() { return new BFS(); }
96
97namespace {
98  class BFSBlockDFSContents : public WorkList {
99    std::deque<WorkListUnit> Queue;
100    SmallVector<WorkListUnit,20> Stack;
101  public:
102    virtual bool hasWork() const {
103      return !Queue.empty() || !Stack.empty();
104    }
105
106    virtual void enqueue(const WorkListUnit& U) {
107      if (isa<BlockEntrance>(U.getNode()->getLocation()))
108        Queue.push_front(U);
109      else
110        Stack.push_back(U);
111    }
112
113    virtual WorkListUnit dequeue() {
114      // Process all basic blocks to completion.
115      if (!Stack.empty()) {
116        const WorkListUnit& U = Stack.back();
117        Stack.pop_back(); // This technically "invalidates" U, but we are fine.
118        return U;
119      }
120
121      assert(!Queue.empty());
122      // Don't use const reference.  The subsequent pop_back() might make it
123      // unsafe.
124      WorkListUnit U = Queue.front();
125      Queue.pop_front();
126      return U;
127    }
128    virtual bool visitItemsInWorkList(Visitor &V) {
129      for (SmallVectorImpl<WorkListUnit>::iterator
130           I = Stack.begin(), E = Stack.end(); I != E; ++I) {
131        if (V.visit(*I))
132          return true;
133      }
134      for (std::deque<WorkListUnit>::iterator
135           I = Queue.begin(), E = Queue.end(); I != E; ++I) {
136        if (V.visit(*I))
137          return true;
138      }
139      return false;
140    }
141
142  };
143} // end anonymous namespace
144
145WorkList* WorkList::makeBFSBlockDFSContents() {
146  return new BFSBlockDFSContents();
147}
148
149//===----------------------------------------------------------------------===//
150// Core analysis engine.
151//===----------------------------------------------------------------------===//
152
153/// ExecuteWorkList - Run the worklist algorithm for a maximum number of steps.
154bool CoreEngine::ExecuteWorkList(const LocationContext *L, unsigned Steps,
155                                   const ProgramState *InitState) {
156
157  if (G->num_roots() == 0) { // Initialize the analysis by constructing
158    // the root if none exists.
159
160    const CFGBlock *Entry = &(L->getCFG()->getEntry());
161
162    assert (Entry->empty() &&
163            "Entry block must be empty.");
164
165    assert (Entry->succ_size() == 1 &&
166            "Entry block must have 1 successor.");
167
168    // Get the solitary successor.
169    const CFGBlock *Succ = *(Entry->succ_begin());
170
171    // Construct an edge representing the
172    // starting location in the function.
173    BlockEdge StartLoc(Entry, Succ, L);
174
175    // Set the current block counter to being empty.
176    WList->setBlockCounter(BCounterFactory.GetEmptyCounter());
177
178    if (!InitState)
179      // Generate the root.
180      generateNode(StartLoc, SubEng.getInitialState(L), 0);
181    else
182      generateNode(StartLoc, InitState, 0);
183  }
184
185  // Check if we have a steps limit
186  bool UnlimitedSteps = Steps == 0;
187
188  while (WList->hasWork()) {
189    if (!UnlimitedSteps) {
190      if (Steps == 0)
191        break;
192      --Steps;
193    }
194
195    const WorkListUnit& WU = WList->dequeue();
196
197    // Set the current block counter.
198    WList->setBlockCounter(WU.getBlockCounter());
199
200    // Retrieve the node.
201    ExplodedNode *Node = WU.getNode();
202
203    // Dispatch on the location type.
204    switch (Node->getLocation().getKind()) {
205      case ProgramPoint::BlockEdgeKind:
206        HandleBlockEdge(cast<BlockEdge>(Node->getLocation()), Node);
207        break;
208
209      case ProgramPoint::BlockEntranceKind:
210        HandleBlockEntrance(cast<BlockEntrance>(Node->getLocation()), Node);
211        break;
212
213      case ProgramPoint::BlockExitKind:
214        assert (false && "BlockExit location never occur in forward analysis.");
215        break;
216
217      case ProgramPoint::CallEnterKind:
218        HandleCallEnter(cast<CallEnter>(Node->getLocation()), WU.getBlock(),
219                        WU.getIndex(), Node);
220        break;
221
222      case ProgramPoint::CallExitKind:
223        HandleCallExit(cast<CallExit>(Node->getLocation()), Node);
224        break;
225
226      default:
227        assert(isa<PostStmt>(Node->getLocation()) ||
228               isa<PostInitializer>(Node->getLocation()));
229        HandlePostStmt(WU.getBlock(), WU.getIndex(), Node);
230        break;
231    }
232  }
233
234  SubEng.processEndWorklist(hasWorkRemaining());
235  return WList->hasWork();
236}
237
238void CoreEngine::ExecuteWorkListWithInitialState(const LocationContext *L,
239                                                 unsigned Steps,
240                                                 const ProgramState *InitState,
241                                                 ExplodedNodeSet &Dst) {
242  ExecuteWorkList(L, Steps, InitState);
243  for (SmallVectorImpl<ExplodedNode*>::iterator I = G->EndNodes.begin(),
244                                           E = G->EndNodes.end(); I != E; ++I) {
245    Dst.Add(*I);
246  }
247}
248
249void CoreEngine::HandleCallEnter(const CallEnter &L, const CFGBlock *Block,
250                                   unsigned Index, ExplodedNode *Pred) {
251  CallEnterNodeBuilder Builder(*this, Pred, L.getCallExpr(),
252                                 L.getCalleeContext(), Block, Index);
253  SubEng.processCallEnter(Builder);
254}
255
256void CoreEngine::HandleCallExit(const CallExit &L, ExplodedNode *Pred) {
257  CallExitNodeBuilder Builder(*this, Pred);
258  SubEng.processCallExit(Builder);
259}
260
261void CoreEngine::HandleBlockEdge(const BlockEdge &L, ExplodedNode *Pred) {
262
263  const CFGBlock *Blk = L.getDst();
264  NodeBuilderContext BuilderCtx(*this, Blk, Pred);
265
266  // Check if we are entering the EXIT block.
267  if (Blk == &(L.getLocationContext()->getCFG()->getExit())) {
268
269    assert (L.getLocationContext()->getCFG()->getExit().size() == 0
270            && "EXIT block cannot contain Stmts.");
271
272    // Process the final state transition.
273    SubEng.processEndOfFunction(BuilderCtx);
274
275    // This path is done. Don't enqueue any more nodes.
276    return;
277  }
278
279  // Call into the SubEngine to process entering the CFGBlock.
280  ExplodedNodeSet dstNodes;
281  BlockEntrance BE(Blk, Pred->getLocationContext());
282  NodeBuilderWithSinks nodeBuilder(Pred, dstNodes, BuilderCtx, BE);
283  SubEng.processCFGBlockEntrance(nodeBuilder);
284
285  // Auto-generate a node.
286  if (!nodeBuilder.hasGeneratedNodes()) {
287    nodeBuilder.generateNode(Pred->State, Pred);
288  }
289
290  // Enqueue nodes onto the worklist.
291  enqueue(dstNodes);
292
293  // Make sink nodes as exhausted.
294  const SmallVectorImpl<ExplodedNode*> &Sinks =  nodeBuilder.getSinks();
295  for (SmallVectorImpl<ExplodedNode*>::const_iterator
296         I =Sinks.begin(), E = Sinks.end(); I != E; ++I) {
297    blocksExhausted.push_back(std::make_pair(L, *I));
298  }
299}
300
301void CoreEngine::HandleBlockEntrance(const BlockEntrance &L,
302                                       ExplodedNode *Pred) {
303
304  // Increment the block counter.
305  BlockCounter Counter = WList->getBlockCounter();
306  Counter = BCounterFactory.IncrementCount(Counter,
307                             Pred->getLocationContext()->getCurrentStackFrame(),
308                                           L.getBlock()->getBlockID());
309  WList->setBlockCounter(Counter);
310
311  // Process the entrance of the block.
312  if (CFGElement E = L.getFirstElement()) {
313    NodeBuilderContext Ctx(*this, L.getBlock(), Pred);
314    SubEng.processCFGElement(E, Pred, 0, &Ctx);
315  }
316  else
317    HandleBlockExit(L.getBlock(), Pred);
318}
319
320void CoreEngine::HandleBlockExit(const CFGBlock * B, ExplodedNode *Pred) {
321
322  if (const Stmt *Term = B->getTerminator()) {
323    switch (Term->getStmtClass()) {
324      default:
325        llvm_unreachable("Analysis for this terminator not implemented.");
326
327      case Stmt::BinaryOperatorClass: // '&&' and '||'
328        HandleBranch(cast<BinaryOperator>(Term)->getLHS(), Term, B, Pred);
329        return;
330
331      case Stmt::BinaryConditionalOperatorClass:
332      case Stmt::ConditionalOperatorClass:
333        HandleBranch(cast<AbstractConditionalOperator>(Term)->getCond(),
334                     Term, B, Pred);
335        return;
336
337        // FIXME: Use constant-folding in CFG construction to simplify this
338        // case.
339
340      case Stmt::ChooseExprClass:
341        HandleBranch(cast<ChooseExpr>(Term)->getCond(), Term, B, Pred);
342        return;
343
344      case Stmt::DoStmtClass:
345        HandleBranch(cast<DoStmt>(Term)->getCond(), Term, B, Pred);
346        return;
347
348      case Stmt::CXXForRangeStmtClass:
349        HandleBranch(cast<CXXForRangeStmt>(Term)->getCond(), Term, B, Pred);
350        return;
351
352      case Stmt::ForStmtClass:
353        HandleBranch(cast<ForStmt>(Term)->getCond(), Term, B, Pred);
354        return;
355
356      case Stmt::ContinueStmtClass:
357      case Stmt::BreakStmtClass:
358      case Stmt::GotoStmtClass:
359        break;
360
361      case Stmt::IfStmtClass:
362        HandleBranch(cast<IfStmt>(Term)->getCond(), Term, B, Pred);
363        return;
364
365      case Stmt::IndirectGotoStmtClass: {
366        // Only 1 successor: the indirect goto dispatch block.
367        assert (B->succ_size() == 1);
368
369        IndirectGotoNodeBuilder
370           builder(Pred, B, cast<IndirectGotoStmt>(Term)->getTarget(),
371                   *(B->succ_begin()), this);
372
373        SubEng.processIndirectGoto(builder);
374        return;
375      }
376
377      case Stmt::ObjCForCollectionStmtClass: {
378        // In the case of ObjCForCollectionStmt, it appears twice in a CFG:
379        //
380        //  (1) inside a basic block, which represents the binding of the
381        //      'element' variable to a value.
382        //  (2) in a terminator, which represents the branch.
383        //
384        // For (1), subengines will bind a value (i.e., 0 or 1) indicating
385        // whether or not collection contains any more elements.  We cannot
386        // just test to see if the element is nil because a container can
387        // contain nil elements.
388        HandleBranch(Term, Term, B, Pred);
389        return;
390      }
391
392      case Stmt::SwitchStmtClass: {
393        SwitchNodeBuilder builder(Pred, B, cast<SwitchStmt>(Term)->getCond(),
394                                    this);
395
396        SubEng.processSwitch(builder);
397        return;
398      }
399
400      case Stmt::WhileStmtClass:
401        HandleBranch(cast<WhileStmt>(Term)->getCond(), Term, B, Pred);
402        return;
403    }
404  }
405
406  assert (B->succ_size() == 1 &&
407          "Blocks with no terminator should have at most 1 successor.");
408
409  generateNode(BlockEdge(B, *(B->succ_begin()), Pred->getLocationContext()),
410               Pred->State, Pred);
411}
412
413void CoreEngine::HandleBranch(const Stmt *Cond, const Stmt *Term,
414                                const CFGBlock * B, ExplodedNode *Pred) {
415  assert(B->succ_size() == 2);
416  NodeBuilderContext Ctx(*this, B, Pred);
417  ExplodedNodeSet Dst;
418  SubEng.processBranch(Cond, Term, Ctx, Pred, Dst,
419                       *(B->succ_begin()), *(B->succ_begin()+1));
420  // Enqueue the new frontier onto the worklist.
421  enqueue(Dst);
422}
423
424void CoreEngine::HandlePostStmt(const CFGBlock *B, unsigned StmtIdx,
425                                  ExplodedNode *Pred) {
426  assert(B);
427  assert(!B->empty());
428
429  if (StmtIdx == B->size())
430    HandleBlockExit(B, Pred);
431  else {
432    NodeBuilderContext Ctx(*this, B, Pred);
433    SubEng.processCFGElement((*B)[StmtIdx], Pred, StmtIdx, &Ctx);
434  }
435}
436
437/// generateNode - Utility method to generate nodes, hook up successors,
438///  and add nodes to the worklist.
439void CoreEngine::generateNode(const ProgramPoint &Loc,
440                              const ProgramState *State,
441                              ExplodedNode *Pred) {
442
443  bool IsNew;
444  ExplodedNode *Node = G->getNode(Loc, State, &IsNew);
445
446  if (Pred)
447    Node->addPredecessor(Pred, *G);  // Link 'Node' with its predecessor.
448  else {
449    assert (IsNew);
450    G->addRoot(Node);  // 'Node' has no predecessor.  Make it a root.
451  }
452
453  // Only add 'Node' to the worklist if it was freshly generated.
454  if (IsNew) WList->enqueue(Node);
455}
456
457void CoreEngine::enqueueStmtNode(ExplodedNode *N,
458                                 const CFGBlock *Block, unsigned Idx) {
459  assert (!N->isSink());
460
461  // Check if this node entered a callee.
462  if (isa<CallEnter>(N->getLocation())) {
463    // Still use the index of the CallExpr. It's needed to create the callee
464    // StackFrameContext.
465    WList->enqueue(N, Block, Idx);
466    return;
467  }
468
469  // Do not create extra nodes. Move to the next CFG element.
470  if (isa<PostInitializer>(N->getLocation())) {
471    WList->enqueue(N, Block, Idx+1);
472    return;
473  }
474
475  const CFGStmt *CS = (*Block)[Idx].getAs<CFGStmt>();
476  const Stmt *St = CS ? CS->getStmt() : 0;
477  PostStmt Loc(St, N->getLocationContext());
478
479  if (Loc == N->getLocation()) {
480    // Note: 'N' should be a fresh node because otherwise it shouldn't be
481    // a member of Deferred.
482    WList->enqueue(N, Block, Idx+1);
483    return;
484  }
485
486  bool IsNew;
487  ExplodedNode *Succ = G->getNode(Loc, N->getState(), &IsNew);
488  Succ->addPredecessor(N, *G);
489
490  if (IsNew)
491    WList->enqueue(Succ, Block, Idx+1);
492}
493
494void CoreEngine::enqueue(ExplodedNodeSet &Set) {
495  for (ExplodedNodeSet::iterator I = Set.begin(),
496                                 E = Set.end(); I != E; ++I) {
497    WList->enqueue(*I);
498  }
499}
500
501void CoreEngine::enqueue(ExplodedNodeSet &Set,
502                         const CFGBlock *Block, unsigned Idx) {
503  for (ExplodedNodeSet::iterator I = Set.begin(),
504                                 E = Set.end(); I != E; ++I) {
505    enqueueStmtNode(*I, Block, Idx);
506  }
507}
508
509
510ExplodedNode* NodeBuilder::generateNodeImpl(const ProgramPoint &Loc,
511                                            const ProgramState *State,
512                                            ExplodedNode *FromN,
513                                            bool MarkAsSink) {
514  HasGeneratedNodes = true;
515  bool IsNew;
516  ExplodedNode *N = C.Eng.G->getNode(Loc, State, &IsNew);
517  N->addPredecessor(FromN, *C.Eng.G);
518  Frontier.erase(FromN);
519
520  if (MarkAsSink)
521    N->markAsSink();
522
523  if (IsNew && !MarkAsSink)
524    Frontier.Add(N);
525
526  return (IsNew ? N : 0);
527}
528
529StmtNodeBuilder::~StmtNodeBuilder() {
530  if (EnclosingBldr)
531    for (ExplodedNodeSet::iterator I = Frontier.begin(),
532                                   E = Frontier.end(); I != E; ++I )
533      EnclosingBldr->addNodes(*I);
534}
535
536ExplodedNode *BranchNodeBuilder::generateNode(const ProgramState *State,
537                                              bool branch,
538                                              ExplodedNode *NodePred) {
539  // If the branch has been marked infeasible we should not generate a node.
540  if (!isFeasible(branch))
541    return NULL;
542
543  ProgramPoint Loc = BlockEdge(C.Block, branch ? DstT:DstF,
544                               NodePred->getLocationContext());
545  ExplodedNode *Succ = generateNodeImpl(Loc, State, NodePred);
546  return Succ;
547}
548
549ExplodedNode*
550IndirectGotoNodeBuilder::generateNode(const iterator &I,
551                                      const ProgramState *St,
552                                      bool isSink) {
553  bool IsNew;
554
555  ExplodedNode *Succ = Eng.G->getNode(BlockEdge(Src, I.getBlock(),
556                                      Pred->getLocationContext()), St, &IsNew);
557
558  Succ->addPredecessor(Pred, *Eng.G);
559
560  if (IsNew) {
561
562    if (isSink)
563      Succ->markAsSink();
564    else
565      Eng.WList->enqueue(Succ);
566
567    return Succ;
568  }
569
570  return NULL;
571}
572
573
574ExplodedNode*
575SwitchNodeBuilder::generateCaseStmtNode(const iterator &I,
576                                        const ProgramState *St) {
577
578  bool IsNew;
579  ExplodedNode *Succ = Eng.G->getNode(BlockEdge(Src, I.getBlock(),
580                                      Pred->getLocationContext()),
581                                      St, &IsNew);
582  Succ->addPredecessor(Pred, *Eng.G);
583  if (IsNew) {
584    Eng.WList->enqueue(Succ);
585    return Succ;
586  }
587  return NULL;
588}
589
590
591ExplodedNode*
592SwitchNodeBuilder::generateDefaultCaseNode(const ProgramState *St,
593                                           bool isSink) {
594  // Get the block for the default case.
595  assert(Src->succ_rbegin() != Src->succ_rend());
596  CFGBlock *DefaultBlock = *Src->succ_rbegin();
597
598  // Sanity check for default blocks that are unreachable and not caught
599  // by earlier stages.
600  if (!DefaultBlock)
601    return NULL;
602
603  bool IsNew;
604
605  ExplodedNode *Succ = Eng.G->getNode(BlockEdge(Src, DefaultBlock,
606                                      Pred->getLocationContext()), St, &IsNew);
607  Succ->addPredecessor(Pred, *Eng.G);
608
609  if (IsNew) {
610    if (isSink)
611      Succ->markAsSink();
612    else
613      Eng.WList->enqueue(Succ);
614
615    return Succ;
616  }
617
618  return NULL;
619}
620
621void CallEnterNodeBuilder::generateNode(const ProgramState *state) {
622  // Check if the callee is in the same translation unit.
623  if (CalleeCtx->getTranslationUnit() !=
624      Pred->getLocationContext()->getTranslationUnit()) {
625    // Create a new engine. We must be careful that the new engine should not
626    // reference data structures owned by the old engine.
627
628    AnalysisManager &OldMgr = Eng.SubEng.getAnalysisManager();
629
630    // Get the callee's translation unit.
631    idx::TranslationUnit *TU = CalleeCtx->getTranslationUnit();
632
633    // Create a new AnalysisManager with components of the callee's
634    // TranslationUnit.
635    // The Diagnostic is  actually shared when we create ASTUnits from AST files.
636    AnalysisManager AMgr(TU->getASTContext(), TU->getDiagnostic(), OldMgr);
637
638    // Create the new engine.
639    // FIXME: This cast isn't really safe.
640    bool GCEnabled = static_cast<ExprEngine&>(Eng.SubEng).isObjCGCEnabled();
641    ExprEngine NewEng(AMgr, GCEnabled);
642
643    // Create the new LocationContext.
644    AnalysisDeclContext *NewAnaCtx =
645      AMgr.getAnalysisDeclContext(CalleeCtx->getDecl(),
646                              CalleeCtx->getTranslationUnit());
647
648    const StackFrameContext *OldLocCtx = CalleeCtx;
649    const StackFrameContext *NewLocCtx =
650      NewAnaCtx->getStackFrame(OldLocCtx->getParent(),
651                               OldLocCtx->getCallSite(),
652                               OldLocCtx->getCallSiteBlock(),
653                               OldLocCtx->getIndex());
654
655    // Now create an initial state for the new engine.
656    const ProgramState *NewState =
657      NewEng.getStateManager().MarshalState(state, NewLocCtx);
658    ExplodedNodeSet ReturnNodes;
659    NewEng.ExecuteWorkListWithInitialState(NewLocCtx, AMgr.getMaxNodes(),
660                                           NewState, ReturnNodes);
661    return;
662  }
663
664  // Get the callee entry block.
665  const CFGBlock *Entry = &(CalleeCtx->getCFG()->getEntry());
666  assert(Entry->empty());
667  assert(Entry->succ_size() == 1);
668
669  // Get the solitary successor.
670  const CFGBlock *SuccB = *(Entry->succ_begin());
671
672  // Construct an edge representing the starting location in the callee.
673  BlockEdge Loc(Entry, SuccB, CalleeCtx);
674
675  bool isNew;
676  ExplodedNode *Node = Eng.G->getNode(Loc, state, &isNew);
677  Node->addPredecessor(const_cast<ExplodedNode*>(Pred), *Eng.G);
678
679  if (isNew)
680    Eng.WList->enqueue(Node);
681}
682
683void CallExitNodeBuilder::generateNode(const ProgramState *state) {
684  // Get the callee's location context.
685  const StackFrameContext *LocCtx
686                         = cast<StackFrameContext>(Pred->getLocationContext());
687  // When exiting an implicit automatic obj dtor call, the callsite is the Stmt
688  // that triggers the dtor.
689  PostStmt Loc(LocCtx->getCallSite(), LocCtx->getParent());
690  bool isNew;
691  ExplodedNode *Node = Eng.G->getNode(Loc, state, &isNew);
692  Node->addPredecessor(const_cast<ExplodedNode*>(Pred), *Eng.G);
693  if (isNew)
694    Eng.WList->enqueue(Node, LocCtx->getCallSiteBlock(),
695                       LocCtx->getIndex() + 1);
696}
697