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      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/CoreEngine.h"
     16 #include "clang/AST/Expr.h"
     17 #include "clang/AST/ExprCXX.h"
     18 #include "clang/AST/StmtCXX.h"
     19 #include "clang/StaticAnalyzer/Core/PathSensitive/AnalysisManager.h"
     20 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
     21 #include "llvm/ADT/DenseMap.h"
     22 #include "llvm/ADT/Statistic.h"
     23 #include "llvm/Support/Casting.h"
     24 
     25 using namespace clang;
     26 using namespace ento;
     27 
     28 #define DEBUG_TYPE "CoreEngine"
     29 
     30 STATISTIC(NumSteps,
     31             "The # of steps executed.");
     32 STATISTIC(NumReachedMaxSteps,
     33             "The # of times we reached the max number of steps.");
     34 STATISTIC(NumPathsExplored,
     35             "The # of paths explored by the analyzer.");
     36 
     37 //===----------------------------------------------------------------------===//
     38 // Worklist classes for exploration of reachable states.
     39 //===----------------------------------------------------------------------===//
     40 
     41 WorkList::Visitor::~Visitor() {}
     42 
     43 namespace {
     44 class DFS : public WorkList {
     45   SmallVector<WorkListUnit,20> Stack;
     46 public:
     47   bool hasWork() const override {
     48     return !Stack.empty();
     49   }
     50 
     51   void enqueue(const WorkListUnit& U) override {
     52     Stack.push_back(U);
     53   }
     54 
     55   WorkListUnit dequeue() override {
     56     assert (!Stack.empty());
     57     const WorkListUnit& U = Stack.back();
     58     Stack.pop_back(); // This technically "invalidates" U, but we are fine.
     59     return U;
     60   }
     61 
     62   bool visitItemsInWorkList(Visitor &V) override {
     63     for (SmallVectorImpl<WorkListUnit>::iterator
     64          I = Stack.begin(), E = Stack.end(); I != E; ++I) {
     65       if (V.visit(*I))
     66         return true;
     67     }
     68     return false;
     69   }
     70 };
     71 
     72 class BFS : public WorkList {
     73   std::deque<WorkListUnit> Queue;
     74 public:
     75   bool hasWork() const override {
     76     return !Queue.empty();
     77   }
     78 
     79   void enqueue(const WorkListUnit& U) override {
     80     Queue.push_back(U);
     81   }
     82 
     83   WorkListUnit dequeue() override {
     84     WorkListUnit U = Queue.front();
     85     Queue.pop_front();
     86     return U;
     87   }
     88 
     89   bool visitItemsInWorkList(Visitor &V) override {
     90     for (std::deque<WorkListUnit>::iterator
     91          I = Queue.begin(), E = Queue.end(); I != E; ++I) {
     92       if (V.visit(*I))
     93         return true;
     94     }
     95     return false;
     96   }
     97 };
     98 
     99 } // end anonymous namespace
    100 
    101 // Place the dstor for WorkList here because it contains virtual member
    102 // functions, and we the code for the dstor generated in one compilation unit.
    103 WorkList::~WorkList() {}
    104 
    105 WorkList *WorkList::makeDFS() { return new DFS(); }
    106 WorkList *WorkList::makeBFS() { return new BFS(); }
    107 
    108 namespace {
    109   class BFSBlockDFSContents : public WorkList {
    110     std::deque<WorkListUnit> Queue;
    111     SmallVector<WorkListUnit,20> Stack;
    112   public:
    113     bool hasWork() const override {
    114       return !Queue.empty() || !Stack.empty();
    115     }
    116 
    117     void enqueue(const WorkListUnit& U) override {
    118       if (U.getNode()->getLocation().getAs<BlockEntrance>())
    119         Queue.push_front(U);
    120       else
    121         Stack.push_back(U);
    122     }
    123 
    124     WorkListUnit dequeue() override {
    125       // Process all basic blocks to completion.
    126       if (!Stack.empty()) {
    127         const WorkListUnit& U = Stack.back();
    128         Stack.pop_back(); // This technically "invalidates" U, but we are fine.
    129         return U;
    130       }
    131 
    132       assert(!Queue.empty());
    133       // Don't use const reference.  The subsequent pop_back() might make it
    134       // unsafe.
    135       WorkListUnit U = Queue.front();
    136       Queue.pop_front();
    137       return U;
    138     }
    139     bool visitItemsInWorkList(Visitor &V) override {
    140       for (SmallVectorImpl<WorkListUnit>::iterator
    141            I = Stack.begin(), E = Stack.end(); I != E; ++I) {
    142         if (V.visit(*I))
    143           return true;
    144       }
    145       for (std::deque<WorkListUnit>::iterator
    146            I = Queue.begin(), E = Queue.end(); I != E; ++I) {
    147         if (V.visit(*I))
    148           return true;
    149       }
    150       return false;
    151     }
    152 
    153   };
    154 } // end anonymous namespace
    155 
    156 WorkList* WorkList::makeBFSBlockDFSContents() {
    157   return new BFSBlockDFSContents();
    158 }
    159 
    160 //===----------------------------------------------------------------------===//
    161 // Core analysis engine.
    162 //===----------------------------------------------------------------------===//
    163 
    164 /// ExecuteWorkList - Run the worklist algorithm for a maximum number of steps.
    165 bool CoreEngine::ExecuteWorkList(const LocationContext *L, unsigned Steps,
    166                                    ProgramStateRef InitState) {
    167 
    168   if (G.num_roots() == 0) { // Initialize the analysis by constructing
    169     // the root if none exists.
    170 
    171     const CFGBlock *Entry = &(L->getCFG()->getEntry());
    172 
    173     assert (Entry->empty() &&
    174             "Entry block must be empty.");
    175 
    176     assert (Entry->succ_size() == 1 &&
    177             "Entry block must have 1 successor.");
    178 
    179     // Mark the entry block as visited.
    180     FunctionSummaries->markVisitedBasicBlock(Entry->getBlockID(),
    181                                              L->getDecl(),
    182                                              L->getCFG()->getNumBlockIDs());
    183 
    184     // Get the solitary successor.
    185     const CFGBlock *Succ = *(Entry->succ_begin());
    186 
    187     // Construct an edge representing the
    188     // starting location in the function.
    189     BlockEdge StartLoc(Entry, Succ, L);
    190 
    191     // Set the current block counter to being empty.
    192     WList->setBlockCounter(BCounterFactory.GetEmptyCounter());
    193 
    194     if (!InitState)
    195       InitState = SubEng.getInitialState(L);
    196 
    197     bool IsNew;
    198     ExplodedNode *Node = G.getNode(StartLoc, InitState, false, &IsNew);
    199     assert (IsNew);
    200     G.addRoot(Node);
    201 
    202     NodeBuilderContext BuilderCtx(*this, StartLoc.getDst(), Node);
    203     ExplodedNodeSet DstBegin;
    204     SubEng.processBeginOfFunction(BuilderCtx, Node, DstBegin, StartLoc);
    205 
    206     enqueue(DstBegin);
    207   }
    208 
    209   // Check if we have a steps limit
    210   bool UnlimitedSteps = Steps == 0;
    211   // Cap our pre-reservation in the event that the user specifies
    212   // a very large number of maximum steps.
    213   const unsigned PreReservationCap = 4000000;
    214   if(!UnlimitedSteps)
    215     G.reserve(std::min(Steps,PreReservationCap));
    216 
    217   while (WList->hasWork()) {
    218     if (!UnlimitedSteps) {
    219       if (Steps == 0) {
    220         NumReachedMaxSteps++;
    221         break;
    222       }
    223       --Steps;
    224     }
    225 
    226     NumSteps++;
    227 
    228     const WorkListUnit& WU = WList->dequeue();
    229 
    230     // Set the current block counter.
    231     WList->setBlockCounter(WU.getBlockCounter());
    232 
    233     // Retrieve the node.
    234     ExplodedNode *Node = WU.getNode();
    235 
    236     dispatchWorkItem(Node, Node->getLocation(), WU);
    237   }
    238   SubEng.processEndWorklist(hasWorkRemaining());
    239   return WList->hasWork();
    240 }
    241 
    242 void CoreEngine::dispatchWorkItem(ExplodedNode* Pred, ProgramPoint Loc,
    243                                   const WorkListUnit& WU) {
    244   // Dispatch on the location type.
    245   switch (Loc.getKind()) {
    246     case ProgramPoint::BlockEdgeKind:
    247       HandleBlockEdge(Loc.castAs<BlockEdge>(), Pred);
    248       break;
    249 
    250     case ProgramPoint::BlockEntranceKind:
    251       HandleBlockEntrance(Loc.castAs<BlockEntrance>(), Pred);
    252       break;
    253 
    254     case ProgramPoint::BlockExitKind:
    255       assert (false && "BlockExit location never occur in forward analysis.");
    256       break;
    257 
    258     case ProgramPoint::CallEnterKind: {
    259       HandleCallEnter(Loc.castAs<CallEnter>(), Pred);
    260       break;
    261     }
    262 
    263     case ProgramPoint::CallExitBeginKind:
    264       SubEng.processCallExit(Pred);
    265       break;
    266 
    267     case ProgramPoint::EpsilonKind: {
    268       assert(Pred->hasSinglePred() &&
    269              "Assume epsilon has exactly one predecessor by construction");
    270       ExplodedNode *PNode = Pred->getFirstPred();
    271       dispatchWorkItem(Pred, PNode->getLocation(), WU);
    272       break;
    273     }
    274     default:
    275       assert(Loc.getAs<PostStmt>() ||
    276              Loc.getAs<PostInitializer>() ||
    277              Loc.getAs<PostImplicitCall>() ||
    278              Loc.getAs<CallExitEnd>());
    279       HandlePostStmt(WU.getBlock(), WU.getIndex(), Pred);
    280       break;
    281   }
    282 }
    283 
    284 bool CoreEngine::ExecuteWorkListWithInitialState(const LocationContext *L,
    285                                                  unsigned Steps,
    286                                                  ProgramStateRef InitState,
    287                                                  ExplodedNodeSet &Dst) {
    288   bool DidNotFinish = ExecuteWorkList(L, Steps, InitState);
    289   for (ExplodedGraph::eop_iterator I = G.eop_begin(), E = G.eop_end(); I != E;
    290        ++I) {
    291     Dst.Add(*I);
    292   }
    293   return DidNotFinish;
    294 }
    295 
    296 void CoreEngine::HandleBlockEdge(const BlockEdge &L, ExplodedNode *Pred) {
    297 
    298   const CFGBlock *Blk = L.getDst();
    299   NodeBuilderContext BuilderCtx(*this, Blk, Pred);
    300 
    301   // Mark this block as visited.
    302   const LocationContext *LC = Pred->getLocationContext();
    303   FunctionSummaries->markVisitedBasicBlock(Blk->getBlockID(),
    304                                            LC->getDecl(),
    305                                            LC->getCFG()->getNumBlockIDs());
    306 
    307   // Check if we are entering the EXIT block.
    308   if (Blk == &(L.getLocationContext()->getCFG()->getExit())) {
    309 
    310     assert (L.getLocationContext()->getCFG()->getExit().size() == 0
    311             && "EXIT block cannot contain Stmts.");
    312 
    313     // Process the final state transition.
    314     SubEng.processEndOfFunction(BuilderCtx, Pred);
    315 
    316     // This path is done. Don't enqueue any more nodes.
    317     return;
    318   }
    319 
    320   // Call into the SubEngine to process entering the CFGBlock.
    321   ExplodedNodeSet dstNodes;
    322   BlockEntrance BE(Blk, Pred->getLocationContext());
    323   NodeBuilderWithSinks nodeBuilder(Pred, dstNodes, BuilderCtx, BE);
    324   SubEng.processCFGBlockEntrance(L, nodeBuilder, Pred);
    325 
    326   // Auto-generate a node.
    327   if (!nodeBuilder.hasGeneratedNodes()) {
    328     nodeBuilder.generateNode(Pred->State, Pred);
    329   }
    330 
    331   // Enqueue nodes onto the worklist.
    332   enqueue(dstNodes);
    333 }
    334 
    335 void CoreEngine::HandleBlockEntrance(const BlockEntrance &L,
    336                                        ExplodedNode *Pred) {
    337 
    338   // Increment the block counter.
    339   const LocationContext *LC = Pred->getLocationContext();
    340   unsigned BlockId = L.getBlock()->getBlockID();
    341   BlockCounter Counter = WList->getBlockCounter();
    342   Counter = BCounterFactory.IncrementCount(Counter, LC->getCurrentStackFrame(),
    343                                            BlockId);
    344   WList->setBlockCounter(Counter);
    345 
    346   // Process the entrance of the block.
    347   if (Optional<CFGElement> E = L.getFirstElement()) {
    348     NodeBuilderContext Ctx(*this, L.getBlock(), Pred);
    349     SubEng.processCFGElement(*E, Pred, 0, &Ctx);
    350   }
    351   else
    352     HandleBlockExit(L.getBlock(), Pred);
    353 }
    354 
    355 void CoreEngine::HandleBlockExit(const CFGBlock * B, ExplodedNode *Pred) {
    356 
    357   if (const Stmt *Term = B->getTerminator()) {
    358     switch (Term->getStmtClass()) {
    359       default:
    360         llvm_unreachable("Analysis for this terminator not implemented.");
    361 
    362       case Stmt::CXXBindTemporaryExprClass:
    363         HandleCleanupTemporaryBranch(
    364             cast<CXXBindTemporaryExpr>(B->getTerminator().getStmt()), B, Pred);
    365         return;
    366 
    367       // Model static initializers.
    368       case Stmt::DeclStmtClass:
    369         HandleStaticInit(cast<DeclStmt>(Term), B, Pred);
    370         return;
    371 
    372       case Stmt::BinaryOperatorClass: // '&&' and '||'
    373         HandleBranch(cast<BinaryOperator>(Term)->getLHS(), Term, B, Pred);
    374         return;
    375 
    376       case Stmt::BinaryConditionalOperatorClass:
    377       case Stmt::ConditionalOperatorClass:
    378         HandleBranch(cast<AbstractConditionalOperator>(Term)->getCond(),
    379                      Term, B, Pred);
    380         return;
    381 
    382         // FIXME: Use constant-folding in CFG construction to simplify this
    383         // case.
    384 
    385       case Stmt::ChooseExprClass:
    386         HandleBranch(cast<ChooseExpr>(Term)->getCond(), Term, B, Pred);
    387         return;
    388 
    389       case Stmt::CXXTryStmtClass: {
    390         // Generate a node for each of the successors.
    391         // Our logic for EH analysis can certainly be improved.
    392         for (CFGBlock::const_succ_iterator it = B->succ_begin(),
    393              et = B->succ_end(); it != et; ++it) {
    394           if (const CFGBlock *succ = *it) {
    395             generateNode(BlockEdge(B, succ, Pred->getLocationContext()),
    396                          Pred->State, Pred);
    397           }
    398         }
    399         return;
    400       }
    401 
    402       case Stmt::DoStmtClass:
    403         HandleBranch(cast<DoStmt>(Term)->getCond(), Term, B, Pred);
    404         return;
    405 
    406       case Stmt::CXXForRangeStmtClass:
    407         HandleBranch(cast<CXXForRangeStmt>(Term)->getCond(), Term, B, Pred);
    408         return;
    409 
    410       case Stmt::ForStmtClass:
    411         HandleBranch(cast<ForStmt>(Term)->getCond(), Term, B, Pred);
    412         return;
    413 
    414       case Stmt::ContinueStmtClass:
    415       case Stmt::BreakStmtClass:
    416       case Stmt::GotoStmtClass:
    417         break;
    418 
    419       case Stmt::IfStmtClass:
    420         HandleBranch(cast<IfStmt>(Term)->getCond(), Term, B, Pred);
    421         return;
    422 
    423       case Stmt::IndirectGotoStmtClass: {
    424         // Only 1 successor: the indirect goto dispatch block.
    425         assert (B->succ_size() == 1);
    426 
    427         IndirectGotoNodeBuilder
    428            builder(Pred, B, cast<IndirectGotoStmt>(Term)->getTarget(),
    429                    *(B->succ_begin()), this);
    430 
    431         SubEng.processIndirectGoto(builder);
    432         return;
    433       }
    434 
    435       case Stmt::ObjCForCollectionStmtClass: {
    436         // In the case of ObjCForCollectionStmt, it appears twice in a CFG:
    437         //
    438         //  (1) inside a basic block, which represents the binding of the
    439         //      'element' variable to a value.
    440         //  (2) in a terminator, which represents the branch.
    441         //
    442         // For (1), subengines will bind a value (i.e., 0 or 1) indicating
    443         // whether or not collection contains any more elements.  We cannot
    444         // just test to see if the element is nil because a container can
    445         // contain nil elements.
    446         HandleBranch(Term, Term, B, Pred);
    447         return;
    448       }
    449 
    450       case Stmt::SwitchStmtClass: {
    451         SwitchNodeBuilder builder(Pred, B, cast<SwitchStmt>(Term)->getCond(),
    452                                     this);
    453 
    454         SubEng.processSwitch(builder);
    455         return;
    456       }
    457 
    458       case Stmt::WhileStmtClass:
    459         HandleBranch(cast<WhileStmt>(Term)->getCond(), Term, B, Pred);
    460         return;
    461     }
    462   }
    463 
    464   assert (B->succ_size() == 1 &&
    465           "Blocks with no terminator should have at most 1 successor.");
    466 
    467   generateNode(BlockEdge(B, *(B->succ_begin()), Pred->getLocationContext()),
    468                Pred->State, Pred);
    469 }
    470 
    471 void CoreEngine::HandleCallEnter(const CallEnter &CE, ExplodedNode *Pred) {
    472   NodeBuilderContext BuilderCtx(*this, CE.getEntry(), Pred);
    473   SubEng.processCallEnter(BuilderCtx, CE, Pred);
    474 }
    475 
    476 void CoreEngine::HandleBranch(const Stmt *Cond, const Stmt *Term,
    477                                 const CFGBlock * B, ExplodedNode *Pred) {
    478   assert(B->succ_size() == 2);
    479   NodeBuilderContext Ctx(*this, B, Pred);
    480   ExplodedNodeSet Dst;
    481   SubEng.processBranch(Cond, Term, Ctx, Pred, Dst,
    482                        *(B->succ_begin()), *(B->succ_begin()+1));
    483   // Enqueue the new frontier onto the worklist.
    484   enqueue(Dst);
    485 }
    486 
    487 void CoreEngine::HandleCleanupTemporaryBranch(const CXXBindTemporaryExpr *BTE,
    488                                               const CFGBlock *B,
    489                                               ExplodedNode *Pred) {
    490   assert(B->succ_size() == 2);
    491   NodeBuilderContext Ctx(*this, B, Pred);
    492   ExplodedNodeSet Dst;
    493   SubEng.processCleanupTemporaryBranch(BTE, Ctx, Pred, Dst, *(B->succ_begin()),
    494                                        *(B->succ_begin() + 1));
    495   // Enqueue the new frontier onto the worklist.
    496   enqueue(Dst);
    497 }
    498 
    499 void CoreEngine::HandleStaticInit(const DeclStmt *DS, const CFGBlock *B,
    500                                   ExplodedNode *Pred) {
    501   assert(B->succ_size() == 2);
    502   NodeBuilderContext Ctx(*this, B, Pred);
    503   ExplodedNodeSet Dst;
    504   SubEng.processStaticInitializer(DS, Ctx, Pred, Dst,
    505                                   *(B->succ_begin()), *(B->succ_begin()+1));
    506   // Enqueue the new frontier onto the worklist.
    507   enqueue(Dst);
    508 }
    509 
    510 
    511 void CoreEngine::HandlePostStmt(const CFGBlock *B, unsigned StmtIdx,
    512                                   ExplodedNode *Pred) {
    513   assert(B);
    514   assert(!B->empty());
    515 
    516   if (StmtIdx == B->size())
    517     HandleBlockExit(B, Pred);
    518   else {
    519     NodeBuilderContext Ctx(*this, B, Pred);
    520     SubEng.processCFGElement((*B)[StmtIdx], Pred, StmtIdx, &Ctx);
    521   }
    522 }
    523 
    524 /// generateNode - Utility method to generate nodes, hook up successors,
    525 ///  and add nodes to the worklist.
    526 void CoreEngine::generateNode(const ProgramPoint &Loc,
    527                               ProgramStateRef State,
    528                               ExplodedNode *Pred) {
    529 
    530   bool IsNew;
    531   ExplodedNode *Node = G.getNode(Loc, State, false, &IsNew);
    532 
    533   if (Pred)
    534     Node->addPredecessor(Pred, G); // Link 'Node' with its predecessor.
    535   else {
    536     assert (IsNew);
    537     G.addRoot(Node); // 'Node' has no predecessor.  Make it a root.
    538   }
    539 
    540   // Only add 'Node' to the worklist if it was freshly generated.
    541   if (IsNew) WList->enqueue(Node);
    542 }
    543 
    544 void CoreEngine::enqueueStmtNode(ExplodedNode *N,
    545                                  const CFGBlock *Block, unsigned Idx) {
    546   assert(Block);
    547   assert (!N->isSink());
    548 
    549   // Check if this node entered a callee.
    550   if (N->getLocation().getAs<CallEnter>()) {
    551     // Still use the index of the CallExpr. It's needed to create the callee
    552     // StackFrameContext.
    553     WList->enqueue(N, Block, Idx);
    554     return;
    555   }
    556 
    557   // Do not create extra nodes. Move to the next CFG element.
    558   if (N->getLocation().getAs<PostInitializer>() ||
    559       N->getLocation().getAs<PostImplicitCall>()) {
    560     WList->enqueue(N, Block, Idx+1);
    561     return;
    562   }
    563 
    564   if (N->getLocation().getAs<EpsilonPoint>()) {
    565     WList->enqueue(N, Block, Idx);
    566     return;
    567   }
    568 
    569   if ((*Block)[Idx].getKind() == CFGElement::NewAllocator) {
    570     WList->enqueue(N, Block, Idx+1);
    571     return;
    572   }
    573 
    574   // At this point, we know we're processing a normal statement.
    575   CFGStmt CS = (*Block)[Idx].castAs<CFGStmt>();
    576   PostStmt Loc(CS.getStmt(), N->getLocationContext());
    577 
    578   if (Loc == N->getLocation().withTag(nullptr)) {
    579     // Note: 'N' should be a fresh node because otherwise it shouldn't be
    580     // a member of Deferred.
    581     WList->enqueue(N, Block, Idx+1);
    582     return;
    583   }
    584 
    585   bool IsNew;
    586   ExplodedNode *Succ = G.getNode(Loc, N->getState(), false, &IsNew);
    587   Succ->addPredecessor(N, G);
    588 
    589   if (IsNew)
    590     WList->enqueue(Succ, Block, Idx+1);
    591 }
    592 
    593 ExplodedNode *CoreEngine::generateCallExitBeginNode(ExplodedNode *N) {
    594   // Create a CallExitBegin node and enqueue it.
    595   const StackFrameContext *LocCtx
    596                          = cast<StackFrameContext>(N->getLocationContext());
    597 
    598   // Use the callee location context.
    599   CallExitBegin Loc(LocCtx);
    600 
    601   bool isNew;
    602   ExplodedNode *Node = G.getNode(Loc, N->getState(), false, &isNew);
    603   Node->addPredecessor(N, G);
    604   return isNew ? Node : nullptr;
    605 }
    606 
    607 
    608 void CoreEngine::enqueue(ExplodedNodeSet &Set) {
    609   for (ExplodedNodeSet::iterator I = Set.begin(),
    610                                  E = Set.end(); I != E; ++I) {
    611     WList->enqueue(*I);
    612   }
    613 }
    614 
    615 void CoreEngine::enqueue(ExplodedNodeSet &Set,
    616                          const CFGBlock *Block, unsigned Idx) {
    617   for (ExplodedNodeSet::iterator I = Set.begin(),
    618                                  E = Set.end(); I != E; ++I) {
    619     enqueueStmtNode(*I, Block, Idx);
    620   }
    621 }
    622 
    623 void CoreEngine::enqueueEndOfFunction(ExplodedNodeSet &Set) {
    624   for (ExplodedNodeSet::iterator I = Set.begin(), E = Set.end(); I != E; ++I) {
    625     ExplodedNode *N = *I;
    626     // If we are in an inlined call, generate CallExitBegin node.
    627     if (N->getLocationContext()->getParent()) {
    628       N = generateCallExitBeginNode(N);
    629       if (N)
    630         WList->enqueue(N);
    631     } else {
    632       // TODO: We should run remove dead bindings here.
    633       G.addEndOfPath(N);
    634       NumPathsExplored++;
    635     }
    636   }
    637 }
    638 
    639 
    640 void NodeBuilder::anchor() { }
    641 
    642 ExplodedNode* NodeBuilder::generateNodeImpl(const ProgramPoint &Loc,
    643                                             ProgramStateRef State,
    644                                             ExplodedNode *FromN,
    645                                             bool MarkAsSink) {
    646   HasGeneratedNodes = true;
    647   bool IsNew;
    648   ExplodedNode *N = C.Eng.G.getNode(Loc, State, MarkAsSink, &IsNew);
    649   N->addPredecessor(FromN, C.Eng.G);
    650   Frontier.erase(FromN);
    651 
    652   if (!IsNew)
    653     return nullptr;
    654 
    655   if (!MarkAsSink)
    656     Frontier.Add(N);
    657 
    658   return N;
    659 }
    660 
    661 void NodeBuilderWithSinks::anchor() { }
    662 
    663 StmtNodeBuilder::~StmtNodeBuilder() {
    664   if (EnclosingBldr)
    665     for (ExplodedNodeSet::iterator I = Frontier.begin(),
    666                                    E = Frontier.end(); I != E; ++I )
    667       EnclosingBldr->addNodes(*I);
    668 }
    669 
    670 void BranchNodeBuilder::anchor() { }
    671 
    672 ExplodedNode *BranchNodeBuilder::generateNode(ProgramStateRef State,
    673                                               bool branch,
    674                                               ExplodedNode *NodePred) {
    675   // If the branch has been marked infeasible we should not generate a node.
    676   if (!isFeasible(branch))
    677     return nullptr;
    678 
    679   ProgramPoint Loc = BlockEdge(C.Block, branch ? DstT:DstF,
    680                                NodePred->getLocationContext());
    681   ExplodedNode *Succ = generateNodeImpl(Loc, State, NodePred);
    682   return Succ;
    683 }
    684 
    685 ExplodedNode*
    686 IndirectGotoNodeBuilder::generateNode(const iterator &I,
    687                                       ProgramStateRef St,
    688                                       bool IsSink) {
    689   bool IsNew;
    690   ExplodedNode *Succ =
    691       Eng.G.getNode(BlockEdge(Src, I.getBlock(), Pred->getLocationContext()),
    692                     St, IsSink, &IsNew);
    693   Succ->addPredecessor(Pred, Eng.G);
    694 
    695   if (!IsNew)
    696     return nullptr;
    697 
    698   if (!IsSink)
    699     Eng.WList->enqueue(Succ);
    700 
    701   return Succ;
    702 }
    703 
    704 
    705 ExplodedNode*
    706 SwitchNodeBuilder::generateCaseStmtNode(const iterator &I,
    707                                         ProgramStateRef St) {
    708 
    709   bool IsNew;
    710   ExplodedNode *Succ =
    711       Eng.G.getNode(BlockEdge(Src, I.getBlock(), Pred->getLocationContext()),
    712                     St, false, &IsNew);
    713   Succ->addPredecessor(Pred, Eng.G);
    714   if (!IsNew)
    715     return nullptr;
    716 
    717   Eng.WList->enqueue(Succ);
    718   return Succ;
    719 }
    720 
    721 
    722 ExplodedNode*
    723 SwitchNodeBuilder::generateDefaultCaseNode(ProgramStateRef St,
    724                                            bool IsSink) {
    725   // Get the block for the default case.
    726   assert(Src->succ_rbegin() != Src->succ_rend());
    727   CFGBlock *DefaultBlock = *Src->succ_rbegin();
    728 
    729   // Sanity check for default blocks that are unreachable and not caught
    730   // by earlier stages.
    731   if (!DefaultBlock)
    732     return nullptr;
    733 
    734   bool IsNew;
    735   ExplodedNode *Succ =
    736       Eng.G.getNode(BlockEdge(Src, DefaultBlock, Pred->getLocationContext()),
    737                     St, IsSink, &IsNew);
    738   Succ->addPredecessor(Pred, Eng.G);
    739 
    740   if (!IsNew)
    741     return nullptr;
    742 
    743   if (!IsSink)
    744     Eng.WList->enqueue(Succ);
    745 
    746   return Succ;
    747 }
    748