clang/lib/StaticAnalyzer/Core/CoreEngine.cpp

   1 //===- CoreEngine.cpp - Path-Sensitive Dataflow Engine --------------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 //  This file defines a generic engine for intraprocedural, path-sensitive,
  10 //  dataflow analysis via graph reachability engine.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "clang/StaticAnalyzer/Core/PathSensitive/CoreEngine.h"
  15 #include "clang/AST/Expr.h"
  16 #include "clang/AST/ExprCXX.h"
  17 #include "clang/AST/Stmt.h"
  18 #include "clang/AST/StmtCXX.h"
  19 #include "clang/Analysis/AnalysisDeclContext.h"
  20 #include "clang/Analysis/CFG.h"
  21 #include "clang/Analysis/ProgramPoint.h"
  22 #include "clang/Basic/LLVM.h"
  23 #include "clang/StaticAnalyzer/Core/AnalyzerOptions.h"
  24 #include "clang/StaticAnalyzer/Core/PathSensitive/BlockCounter.h"
  25 #include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"
  26 #include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
  27 #include "clang/StaticAnalyzer/Core/PathSensitive/FunctionSummary.h"
  28 #include "clang/StaticAnalyzer/Core/PathSensitive/WorkList.h"
  29 #include "llvm/ADT/STLExtras.h"
  30 #include "llvm/ADT/Statistic.h"
  31 #include "llvm/Support/Casting.h"
  32 #include "llvm/Support/ErrorHandling.h"
  33 #include <algorithm>
  34 #include <cassert>
  35 #include <memory>
  36 #include <optional>
  37 #include <utility>
  38
  39 using namespace clang;
  40 using namespace ento;
  41
  42 #define DEBUG_TYPE "CoreEngine"
  43
  44 STATISTIC(NumSteps,
  45             "The # of steps executed.");
  46 STATISTIC(NumSTUSteps, "The # of STU steps executed.");
  47 STATISTIC(NumCTUSteps, "The # of CTU steps executed.");
  48 STATISTIC(NumReachedMaxSteps,
  49             "The # of times we reached the max number of steps.");
  50 STATISTIC(NumPathsExplored,
  51             "The # of paths explored by the analyzer.");
  52
  53 //===----------------------------------------------------------------------===//
  54 // Core analysis engine.
  55 //===----------------------------------------------------------------------===//
  56
  57 static std::unique_ptr<WorkList> generateWorkList(AnalyzerOptions &Opts) {
  58   switch (Opts.getExplorationStrategy()) {
  59     case ExplorationStrategyKind::DFS:
  60       return WorkList::makeDFS();
  61     case ExplorationStrategyKind::BFS:
  62       return WorkList::makeBFS();
  63     case ExplorationStrategyKind::BFSBlockDFSContents:
  64       return WorkList::makeBFSBlockDFSContents();
  65     case ExplorationStrategyKind::UnexploredFirst:
  66       return WorkList::makeUnexploredFirst();
  67     case ExplorationStrategyKind::UnexploredFirstQueue:
  68       return WorkList::makeUnexploredFirstPriorityQueue();
  69     case ExplorationStrategyKind::UnexploredFirstLocationQueue:
  70       return WorkList::makeUnexploredFirstPriorityLocationQueue();
  71   }
  72   llvm_unreachable("Unknown AnalyzerOptions::ExplorationStrategyKind");
  73 }
  74
  75 CoreEngine::CoreEngine(ExprEngine &exprengine, FunctionSummariesTy *FS,
  76                        AnalyzerOptions &Opts)
  77     : ExprEng(exprengine), WList(generateWorkList(Opts)),
  78       CTUWList(Opts.IsNaiveCTUEnabled ? generateWorkList(Opts) : nullptr),
  79       BCounterFactory(G.getAllocator()), FunctionSummaries(FS) {}
  80
  81 void CoreEngine::setBlockCounter(BlockCounter C) {
  82   WList->setBlockCounter(C);
  83   if (CTUWList)
  84     CTUWList->setBlockCounter(C);
  85 }
  86
  87 /// ExecuteWorkList - Run the worklist algorithm for a maximum number of steps.
  88 bool CoreEngine::ExecuteWorkList(const LocationContext *L, unsigned MaxSteps,
  89                                  ProgramStateRef InitState) {
  90   if (G.num_roots() == 0) { // Initialize the analysis by constructing
  91     // the root if none exists.
  92
  93     const CFGBlock *Entry = &(L->getCFG()->getEntry());
  94
  95     assert(Entry->empty() && "Entry block must be empty.");
  96
  97     assert(Entry->succ_size() == 1 && "Entry block must have 1 successor.");
  98
  99     // Mark the entry block as visited.
 100     FunctionSummaries->markVisitedBasicBlock(Entry->getBlockID(),
 101                                              L->getDecl(),
 102                                              L->getCFG()->getNumBlockIDs());
 103
 104     // Get the solitary successor.
 105     const CFGBlock *Succ = *(Entry->succ_begin());
 106
 107     // Construct an edge representing the
 108     // starting location in the function.
 109     BlockEdge StartLoc(Entry, Succ, L);
 110
 111     // Set the current block counter to being empty.
 112     setBlockCounter(BCounterFactory.GetEmptyCounter());
 113
 114     if (!InitState)
 115       InitState = ExprEng.getInitialState(L);
 116
 117     bool IsNew;
 118     ExplodedNode *Node = G.getNode(StartLoc, InitState, false, &IsNew);
 119     assert(IsNew);
 120     G.addRoot(Node);
 121
 122     NodeBuilderContext BuilderCtx(*this, StartLoc.getDst(), Node);
 123     ExplodedNodeSet DstBegin;
 124     ExprEng.processBeginOfFunction(BuilderCtx, Node, DstBegin, StartLoc);
 125
 126     enqueue(DstBegin);
 127   }
 128
 129   // Check if we have a steps limit
 130   bool UnlimitedSteps = MaxSteps == 0;
 131
 132   // Cap our pre-reservation in the event that the user specifies
 133   // a very large number of maximum steps.
 134   const unsigned PreReservationCap = 4000000;
 135   if(!UnlimitedSteps)
 136     G.reserve(std::min(MaxSteps, PreReservationCap));
 137
 138   auto ProcessWList = [this, UnlimitedSteps](unsigned MaxSteps) {
 139     unsigned Steps = MaxSteps;
 140     while (WList->hasWork()) {
 141       if (!UnlimitedSteps) {
 142         if (Steps == 0) {
 143           NumReachedMaxSteps++;
 144           break;
 145         }
 146         --Steps;
 147       }
 148
 149       NumSteps++;
 150
 151       const WorkListUnit &WU = WList->dequeue();
 152
 153       // Set the current block counter.
 154       setBlockCounter(WU.getBlockCounter());
 155
 156       // Retrieve the node.
 157       ExplodedNode *Node = WU.getNode();
 158
 159       dispatchWorkItem(Node, Node->getLocation(), WU);
 160     }
 161     return MaxSteps - Steps;
 162   };
 163   const unsigned STUSteps = ProcessWList(MaxSteps);
 164
 165   if (CTUWList) {
 166     NumSTUSteps += STUSteps;
 167     const unsigned MinCTUSteps =
 168         this->ExprEng.getAnalysisManager().options.CTUMaxNodesMin;
 169     const unsigned Pct =
 170         this->ExprEng.getAnalysisManager().options.CTUMaxNodesPercentage;
 171     unsigned MaxCTUSteps = std::max(STUSteps * Pct / 100, MinCTUSteps);
 172
 173     WList = std::move(CTUWList);
 174     const unsigned CTUSteps = ProcessWList(MaxCTUSteps);
 175     NumCTUSteps += CTUSteps;
 176   }
 177
 178   ExprEng.processEndWorklist();
 179   return WList->hasWork();
 180 }
 181
 182 void CoreEngine::dispatchWorkItem(ExplodedNode* Pred, ProgramPoint Loc,
 183                                   const WorkListUnit& WU) {
 184   // Dispatch on the location type.
 185   switch (Loc.getKind()) {
 186     case ProgramPoint::BlockEdgeKind:
 187       HandleBlockEdge(Loc.castAs<BlockEdge>(), Pred);
 188       break;
 189
 190     case ProgramPoint::BlockEntranceKind:
 191       HandleBlockEntrance(Loc.castAs<BlockEntrance>(), Pred);
 192       break;
 193
 194     case ProgramPoint::BlockExitKind:
 195       assert(false && "BlockExit location never occur in forward analysis.");
 196       break;
 197
 198     case ProgramPoint::CallEnterKind:
 199       HandleCallEnter(Loc.castAs<CallEnter>(), Pred);
 200       break;
 201
 202     case ProgramPoint::CallExitBeginKind:
 203       ExprEng.processCallExit(Pred);
 204       break;
 205
 206     case ProgramPoint::EpsilonKind: {
 207       assert(Pred->hasSinglePred() &&
 208              "Assume epsilon has exactly one predecessor by construction");
 209       ExplodedNode *PNode = Pred->getFirstPred();
 210       dispatchWorkItem(Pred, PNode->getLocation(), WU);
 211       break;
 212     }
 213     default:
 214       assert(Loc.getAs<PostStmt>() ||
 215              Loc.getAs<PostInitializer>() ||
 216              Loc.getAs<PostImplicitCall>() ||
 217              Loc.getAs<CallExitEnd>() ||
 218              Loc.getAs<LoopExit>() ||
 219              Loc.getAs<PostAllocatorCall>());
 220       HandlePostStmt(WU.getBlock(), WU.getIndex(), Pred);
 221       break;
 222   }
 223 }
 224
 225 bool CoreEngine::ExecuteWorkListWithInitialState(const LocationContext *L,
 226                                                  unsigned Steps,
 227                                                  ProgramStateRef InitState,
 228                                                  ExplodedNodeSet &Dst) {
 229   bool DidNotFinish = ExecuteWorkList(L, Steps, InitState);
 230   for (ExplodedGraph::eop_iterator I = G.eop_begin(), E = G.eop_end(); I != E;
 231        ++I) {
 232     Dst.Add(*I);
 233   }
 234   return DidNotFinish;
 235 }
 236
 237 void CoreEngine::HandleBlockEdge(const BlockEdge &L, ExplodedNode *Pred) {
 238   const CFGBlock *Blk = L.getDst();
 239   NodeBuilderContext BuilderCtx(*this, Blk, Pred);
 240
 241   // Mark this block as visited.
 242   const LocationContext *LC = Pred->getLocationContext();
 243   FunctionSummaries->markVisitedBasicBlock(Blk->getBlockID(),
 244                                            LC->getDecl(),
 245                                            LC->getCFG()->getNumBlockIDs());
 246
 247   // Display a prunable path note to the user if it's a virtual bases branch
 248   // and we're taking the path that skips virtual base constructors.
 249   if (L.getSrc()->getTerminator().isVirtualBaseBranch() &&
 250       L.getDst() == *L.getSrc()->succ_begin()) {
 251     ProgramPoint P = L.withTag(getDataTags().make<NoteTag>(
 252         [](BugReporterContext &, PathSensitiveBugReport &) -> std::string {
 253           // TODO: Just call out the name of the most derived class
 254           // when we know it.
 255           return "Virtual base initialization skipped because "
 256                  "it has already been handled by the most derived class";
 257         },
 258         /*IsPrunable=*/true));
 259     // Perform the transition.
 260     ExplodedNodeSet Dst;
 261     NodeBuilder Bldr(Pred, Dst, BuilderCtx);
 262     Pred = Bldr.generateNode(P, Pred->getState(), Pred);
 263     if (!Pred)
 264       return;
 265   }
 266
 267   // Check if we are entering the EXIT block.
 268   if (Blk == &(L.getLocationContext()->getCFG()->getExit())) {
 269     assert(L.getLocationContext()->getCFG()->getExit().empty() &&
 270            "EXIT block cannot contain Stmts.");
 271
 272     // Get return statement..
 273     const ReturnStmt *RS = nullptr;
 274     if (!L.getSrc()->empty()) {
 275       CFGElement LastElement = L.getSrc()->back();
 276       if (std::optional<CFGStmt> LastStmt = LastElement.getAs<CFGStmt>()) {
 277         RS = dyn_cast<ReturnStmt>(LastStmt->getStmt());
 278       } else if (std::optional<CFGAutomaticObjDtor> AutoDtor =
 279                      LastElement.getAs<CFGAutomaticObjDtor>()) {
 280         RS = dyn_cast<ReturnStmt>(AutoDtor->getTriggerStmt());
 281       }
 282     }
 283
 284     // Process the final state transition.
 285     ExprEng.processEndOfFunction(BuilderCtx, Pred, RS);
 286
 287     // This path is done. Don't enqueue any more nodes.
 288     return;
 289   }
 290
 291   // Call into the ExprEngine to process entering the CFGBlock.
 292   ExplodedNodeSet dstNodes;
 293   BlockEntrance BE(Blk, Pred->getLocationContext());
 294   NodeBuilderWithSinks nodeBuilder(Pred, dstNodes, BuilderCtx, BE);
 295   ExprEng.processCFGBlockEntrance(L, nodeBuilder, Pred);
 296
 297   // Auto-generate a node.
 298   if (!nodeBuilder.hasGeneratedNodes()) {
 299     nodeBuilder.generateNode(Pred->State, Pred);
 300   }
 301
 302   // Enqueue nodes onto the worklist.
 303   enqueue(dstNodes);
 304 }
 305
 306 void CoreEngine::HandleBlockEntrance(const BlockEntrance &L,
 307                                        ExplodedNode *Pred) {
 308   // Increment the block counter.
 309   const LocationContext *LC = Pred->getLocationContext();
 310   unsigned BlockId = L.getBlock()->getBlockID();
 311   BlockCounter Counter = WList->getBlockCounter();
 312   Counter = BCounterFactory.IncrementCount(Counter, LC->getStackFrame(),
 313                                            BlockId);
 314   setBlockCounter(Counter);
 315
 316   // Process the entrance of the block.
 317   if (std::optional<CFGElement> E = L.getFirstElement()) {
 318     NodeBuilderContext Ctx(*this, L.getBlock(), Pred);
 319     ExprEng.processCFGElement(*E, Pred, 0, &Ctx);
 320   } else
 321     HandleBlockExit(L.getBlock(), Pred);
 322 }
 323
 324 void CoreEngine::HandleBlockExit(const CFGBlock * B, ExplodedNode *Pred) {
 325   if (const Stmt *Term = B->getTerminatorStmt()) {
 326     switch (Term->getStmtClass()) {
 327       default:
 328         llvm_unreachable("Analysis for this terminator not implemented.");
 329
 330       case Stmt::CXXBindTemporaryExprClass:
 331         HandleCleanupTemporaryBranch(
 332             cast<CXXBindTemporaryExpr>(Term), B, Pred);
 333         return;
 334
 335       // Model static initializers.
 336       case Stmt::DeclStmtClass:
 337         HandleStaticInit(cast<DeclStmt>(Term), B, Pred);
 338         return;
 339
 340       case Stmt::BinaryOperatorClass: // '&&' and '||'
 341         HandleBranch(cast<BinaryOperator>(Term)->getLHS(), Term, B, Pred);
 342         return;
 343
 344       case Stmt::BinaryConditionalOperatorClass:
 345       case Stmt::ConditionalOperatorClass:
 346         HandleBranch(cast<AbstractConditionalOperator>(Term)->getCond(),
 347                      Term, B, Pred);
 348         return;
 349
 350         // FIXME: Use constant-folding in CFG construction to simplify this
 351         // case.
 352
 353       case Stmt::ChooseExprClass:
 354         HandleBranch(cast<ChooseExpr>(Term)->getCond(), Term, B, Pred);
 355         return;
 356
 357       case Stmt::CXXTryStmtClass:
 358         // Generate a node for each of the successors.
 359         // Our logic for EH analysis can certainly be improved.
 360         for (CFGBlock::const_succ_iterator it = B->succ_begin(),
 361              et = B->succ_end(); it != et; ++it) {
 362           if (const CFGBlock *succ = *it) {
 363             generateNode(BlockEdge(B, succ, Pred->getLocationContext()),
 364                          Pred->State, Pred);
 365           }
 366         }
 367         return;
 368
 369       case Stmt::DoStmtClass:
 370         HandleBranch(cast<DoStmt>(Term)->getCond(), Term, B, Pred);
 371         return;
 372
 373       case Stmt::CXXForRangeStmtClass:
 374         HandleBranch(cast<CXXForRangeStmt>(Term)->getCond(), Term, B, Pred);
 375         return;
 376
 377       case Stmt::ForStmtClass:
 378         HandleBranch(cast<ForStmt>(Term)->getCond(), Term, B, Pred);
 379         return;
 380
 381       case Stmt::SEHLeaveStmtClass:
 382       case Stmt::ContinueStmtClass:
 383       case Stmt::BreakStmtClass:
 384       case Stmt::GotoStmtClass:
 385         break;
 386
 387       case Stmt::IfStmtClass:
 388         HandleBranch(cast<IfStmt>(Term)->getCond(), Term, B, Pred);
 389         return;
 390
 391       case Stmt::IndirectGotoStmtClass: {
 392         // Only 1 successor: the indirect goto dispatch block.
 393         assert(B->succ_size() == 1);
 394
 395         IndirectGotoNodeBuilder
 396            builder(Pred, B, cast<IndirectGotoStmt>(Term)->getTarget(),
 397                    *(B->succ_begin()), this);
 398
 399         ExprEng.processIndirectGoto(builder);
 400         return;
 401       }
 402
 403       case Stmt::ObjCForCollectionStmtClass:
 404         // In the case of ObjCForCollectionStmt, it appears twice in a CFG:
 405         //
 406         //  (1) inside a basic block, which represents the binding of the
 407         //      'element' variable to a value.
 408         //  (2) in a terminator, which represents the branch.
 409         //
 410         // For (1), ExprEngine will bind a value (i.e., 0 or 1) indicating
 411         // whether or not collection contains any more elements.  We cannot
 412         // just test to see if the element is nil because a container can
 413         // contain nil elements.
 414         HandleBranch(Term, Term, B, Pred);
 415         return;
 416
 417       case Stmt::SwitchStmtClass: {
 418         SwitchNodeBuilder builder(Pred, B, cast<SwitchStmt>(Term)->getCond(),
 419                                     this);
 420
 421         ExprEng.processSwitch(builder);
 422         return;
 423       }
 424
 425       case Stmt::WhileStmtClass:
 426         HandleBranch(cast<WhileStmt>(Term)->getCond(), Term, B, Pred);
 427         return;
 428
 429       case Stmt::GCCAsmStmtClass:
 430         assert(cast<GCCAsmStmt>(Term)->isAsmGoto() && "Encountered GCCAsmStmt without labels");
 431         // TODO: Handle jumping to labels
 432         return;
 433     }
 434   }
 435
 436   if (B->getTerminator().isVirtualBaseBranch()) {
 437     HandleVirtualBaseBranch(B, Pred);
 438     return;
 439   }
 440
 441   assert(B->succ_size() == 1 &&
 442          "Blocks with no terminator should have at most 1 successor.");
 443
 444   generateNode(BlockEdge(B, *(B->succ_begin()), Pred->getLocationContext()),
 445                Pred->State, Pred);
 446 }
 447
 448 void CoreEngine::HandleCallEnter(const CallEnter &CE, ExplodedNode *Pred) {
 449   NodeBuilderContext BuilderCtx(*this, CE.getEntry(), Pred);
 450   ExprEng.processCallEnter(BuilderCtx, CE, Pred);
 451 }
 452
 453 void CoreEngine::HandleBranch(const Stmt *Cond, const Stmt *Term,
 454                                 const CFGBlock * B, ExplodedNode *Pred) {
 455   assert(B->succ_size() == 2);
 456   NodeBuilderContext Ctx(*this, B, Pred);
 457   ExplodedNodeSet Dst;
 458   ExprEng.processBranch(Cond, Ctx, Pred, Dst, *(B->succ_begin()),
 459                        *(B->succ_begin() + 1));
 460   // Enqueue the new frontier onto the worklist.
 461   enqueue(Dst);
 462 }
 463
 464 void CoreEngine::HandleCleanupTemporaryBranch(const CXXBindTemporaryExpr *BTE,
 465                                               const CFGBlock *B,
 466                                               ExplodedNode *Pred) {
 467   assert(B->succ_size() == 2);
 468   NodeBuilderContext Ctx(*this, B, Pred);
 469   ExplodedNodeSet Dst;
 470   ExprEng.processCleanupTemporaryBranch(BTE, Ctx, Pred, Dst, *(B->succ_begin()),
 471                                        *(B->succ_begin() + 1));
 472   // Enqueue the new frontier onto the worklist.
 473   enqueue(Dst);
 474 }
 475
 476 void CoreEngine::HandleStaticInit(const DeclStmt *DS, const CFGBlock *B,
 477                                   ExplodedNode *Pred) {
 478   assert(B->succ_size() == 2);
 479   NodeBuilderContext Ctx(*this, B, Pred);
 480   ExplodedNodeSet Dst;
 481   ExprEng.processStaticInitializer(DS, 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::HandlePostStmt(const CFGBlock *B, unsigned StmtIdx,
 488                                 ExplodedNode *Pred) {
 489   assert(B);
 490   assert(!B->empty());
 491
 492   if (StmtIdx == B->size())
 493     HandleBlockExit(B, Pred);
 494   else {
 495     NodeBuilderContext Ctx(*this, B, Pred);
 496     ExprEng.processCFGElement((*B)[StmtIdx], Pred, StmtIdx, &Ctx);
 497   }
 498 }
 499
 500 void CoreEngine::HandleVirtualBaseBranch(const CFGBlock *B,
 501                                          ExplodedNode *Pred) {
 502   const LocationContext *LCtx = Pred->getLocationContext();
 503   if (const auto *CallerCtor = dyn_cast_or_null<CXXConstructExpr>(
 504           LCtx->getStackFrame()->getCallSite())) {
 505     switch (CallerCtor->getConstructionKind()) {
 506     case CXXConstructExpr::CK_NonVirtualBase:
 507     case CXXConstructExpr::CK_VirtualBase: {
 508       BlockEdge Loc(B, *B->succ_begin(), LCtx);
 509       HandleBlockEdge(Loc, Pred);
 510       return;
 511     }
 512     default:
 513       break;
 514     }
 515   }
 516
 517   // We either don't see a parent stack frame because we're in the top frame,
 518   // or the parent stack frame doesn't initialize our virtual bases.
 519   BlockEdge Loc(B, *(B->succ_begin() + 1), LCtx);
 520   HandleBlockEdge(Loc, Pred);
 521 }
 522
 523 /// generateNode - Utility method to generate nodes, hook up successors,
 524 ///  and add nodes to the worklist.
 525 void CoreEngine::generateNode(const ProgramPoint &Loc,
 526                               ProgramStateRef State,
 527                               ExplodedNode *Pred) {
 528   bool IsNew;
 529   ExplodedNode *Node = G.getNode(Loc, State, false, &IsNew);
 530
 531   if (Pred)
 532     Node->addPredecessor(Pred, G); // Link 'Node' with its predecessor.
 533   else {
 534     assert(IsNew);
 535     G.addRoot(Node); // 'Node' has no predecessor.  Make it a root.
 536   }
 537
 538   // Only add 'Node' to the worklist if it was freshly generated.
 539   if (IsNew) WList->enqueue(Node);
 540 }
 541
 542 void CoreEngine::enqueueStmtNode(ExplodedNode *N,
 543                                  const CFGBlock *Block, unsigned Idx) {
 544   assert(Block);
 545   assert(!N->isSink());
 546
 547   // Check if this node entered a callee.
 548   if (N->getLocation().getAs<CallEnter>()) {
 549     // Still use the index of the CallExpr. It's needed to create the callee
 550     // StackFrameContext.
 551     WList->enqueue(N, Block, Idx);
 552     return;
 553   }
 554
 555   // Do not create extra nodes. Move to the next CFG element.
 556   if (N->getLocation().getAs<PostInitializer>() ||
 557       N->getLocation().getAs<PostImplicitCall>()||
 558       N->getLocation().getAs<LoopExit>()) {
 559     WList->enqueue(N, Block, Idx+1);
 560     return;
 561   }
 562
 563   if (N->getLocation().getAs<EpsilonPoint>()) {
 564     WList->enqueue(N, Block, Idx);
 565     return;
 566   }
 567
 568   if ((*Block)[Idx].getKind() == CFGElement::NewAllocator) {
 569     WList->enqueue(N, Block, Idx+1);
 570     return;
 571   }
 572
 573   // At this point, we know we're processing a normal statement.
 574   CFGStmt CS = (*Block)[Idx].castAs<CFGStmt>();
 575   PostStmt Loc(CS.getStmt(), N->getLocationContext());
 576
 577   if (Loc == N->getLocation().withTag(nullptr)) {
 578     // Note: 'N' should be a fresh node because otherwise it shouldn't be
 579     // a member of Deferred.
 580     WList->enqueue(N, Block, Idx+1);
 581     return;
 582   }
 583
 584   bool IsNew;
 585   ExplodedNode *Succ = G.getNode(Loc, N->getState(), false, &IsNew);
 586   Succ->addPredecessor(N, G);
 587
 588   if (IsNew)
 589     WList->enqueue(Succ, Block, Idx+1);
 590 }
 591
 592 ExplodedNode *CoreEngine::generateCallExitBeginNode(ExplodedNode *N,
 593                                                     const ReturnStmt *RS) {
 594   // Create a CallExitBegin node and enqueue it.
 595   const auto *LocCtx = cast<StackFrameContext>(N->getLocationContext());
 596
 597   // Use the callee location context.
 598   CallExitBegin Loc(LocCtx, RS);
 599
 600   bool isNew;
 601   ExplodedNode *Node = G.getNode(Loc, N->getState(), false, &isNew);
 602   Node->addPredecessor(N, G);
 603   return isNew ? Node : nullptr;
 604 }
 605
 606 void CoreEngine::enqueue(ExplodedNodeSet &Set) {
 607   for (const auto I : Set)
 608     WList->enqueue(I);
 609 }
 610
 611 void CoreEngine::enqueue(ExplodedNodeSet &Set,
 612                          const CFGBlock *Block, unsigned Idx) {
 613   for (const auto I : Set)
 614     enqueueStmtNode(I, Block, Idx);
 615 }
 616
 617 void CoreEngine::enqueueEndOfFunction(ExplodedNodeSet &Set, const ReturnStmt *RS) {
 618   for (auto *I : Set) {
 619     // If we are in an inlined call, generate CallExitBegin node.
 620     if (I->getLocationContext()->getParent()) {
 621       I = generateCallExitBeginNode(I, RS);
 622       if (I)
 623         WList->enqueue(I);
 624     } else {
 625       // TODO: We should run remove dead bindings here.
 626       G.addEndOfPath(I);
 627       NumPathsExplored++;
 628     }
 629   }
 630 }
 631
 632 void NodeBuilder::anchor() {}
 633
 634 ExplodedNode* NodeBuilder::generateNodeImpl(const ProgramPoint &Loc,
 635                                             ProgramStateRef State,
 636                                             ExplodedNode *FromN,
 637                                             bool MarkAsSink) {
 638   HasGeneratedNodes = true;
 639   bool IsNew;
 640   ExplodedNode *N = C.Eng.G.getNode(Loc, State, MarkAsSink, &IsNew);
 641   N->addPredecessor(FromN, C.Eng.G);
 642   Frontier.erase(FromN);
 643
 644   if (!IsNew)
 645     return nullptr;
 646
 647   if (!MarkAsSink)
 648     Frontier.Add(N);
 649
 650   return N;
 651 }
 652
 653 void NodeBuilderWithSinks::anchor() {}
 654
 655 StmtNodeBuilder::~StmtNodeBuilder() {
 656   if (EnclosingBldr)
 657     for (const auto I : Frontier)
 658       EnclosingBldr->addNodes(I);
 659 }
 660
 661 void BranchNodeBuilder::anchor() {}
 662
 663 ExplodedNode *BranchNodeBuilder::generateNode(ProgramStateRef State,
 664                                               bool branch,
 665                                               ExplodedNode *NodePred) {
 666   // If the branch has been marked infeasible we should not generate a node.
 667   if (!isFeasible(branch))
 668     return nullptr;
 669
 670   ProgramPoint Loc = BlockEdge(C.Block, branch ? DstT:DstF,
 671                                NodePred->getLocationContext());
 672   ExplodedNode *Succ = generateNodeImpl(Loc, State, NodePred);
 673   return Succ;
 674 }
 675
 676 ExplodedNode*
 677 IndirectGotoNodeBuilder::generateNode(const iterator &I,
 678                                       ProgramStateRef St,
 679                                       bool IsSink) {
 680   bool IsNew;
 681   ExplodedNode *Succ =
 682       Eng.G.getNode(BlockEdge(Src, I.getBlock(), Pred->getLocationContext()),
 683                     St, IsSink, &IsNew);
 684   Succ->addPredecessor(Pred, Eng.G);
 685
 686   if (!IsNew)
 687     return nullptr;
 688
 689   if (!IsSink)
 690     Eng.WList->enqueue(Succ);
 691
 692   return Succ;
 693 }
 694
 695 ExplodedNode*
 696 SwitchNodeBuilder::generateCaseStmtNode(const iterator &I,
 697                                         ProgramStateRef St) {
 698   bool IsNew;
 699   ExplodedNode *Succ =
 700       Eng.G.getNode(BlockEdge(Src, I.getBlock(), Pred->getLocationContext()),
 701                     St, false, &IsNew);
 702   Succ->addPredecessor(Pred, Eng.G);
 703   if (!IsNew)
 704     return nullptr;
 705
 706   Eng.WList->enqueue(Succ);
 707   return Succ;
 708 }
 709
 710 ExplodedNode*
 711 SwitchNodeBuilder::generateDefaultCaseNode(ProgramStateRef St,
 712                                            bool IsSink) {
 713   // Get the block for the default case.
 714   assert(Src->succ_rbegin() != Src->succ_rend());
 715   CFGBlock *DefaultBlock = *Src->succ_rbegin();
 716
 717   // Basic correctness check for default blocks that are unreachable and not
 718   // caught by earlier stages.
 719   if (!DefaultBlock)
 720     return nullptr;
 721
 722   bool IsNew;
 723   ExplodedNode *Succ =
 724       Eng.G.getNode(BlockEdge(Src, DefaultBlock, Pred->getLocationContext()),
 725                     St, IsSink, &IsNew);
 726   Succ->addPredecessor(Pred, Eng.G);
 727
 728   if (!IsNew)
 729     return nullptr;
 730
 731   if (!IsSink)
 732     Eng.WList->enqueue(Succ);
 733
 734   return Succ;
 735 }