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 void CoreEngine::HandleBlockEdge(const BlockEdge &L, ExplodedNode *Pred) {
 226   const CFGBlock *Blk = L.getDst();
 227   NodeBuilderContext BuilderCtx(*this, Blk, Pred);
 228
 229   // Mark this block as visited.
 230   const LocationContext *LC = Pred->getLocationContext();
 231   FunctionSummaries->markVisitedBasicBlock(Blk->getBlockID(),
 232                                            LC->getDecl(),
 233                                            LC->getCFG()->getNumBlockIDs());
 234
 235   // Display a prunable path note to the user if it's a virtual bases branch
 236   // and we're taking the path that skips virtual base constructors.
 237   if (L.getSrc()->getTerminator().isVirtualBaseBranch() &&
 238       L.getDst() == *L.getSrc()->succ_begin()) {
 239     ProgramPoint P = L.withTag(getDataTags().make<NoteTag>(
 240         [](BugReporterContext &, PathSensitiveBugReport &) -> std::string {
 241           // TODO: Just call out the name of the most derived class
 242           // when we know it.
 243           return "Virtual base initialization skipped because "
 244                  "it has already been handled by the most derived class";
 245         },
 246         /*IsPrunable=*/true));
 247     // Perform the transition.
 248     ExplodedNodeSet Dst;
 249     NodeBuilder Bldr(Pred, Dst, BuilderCtx);
 250     Pred = Bldr.generateNode(P, Pred->getState(), Pred);
 251     if (!Pred)
 252       return;
 253   }
 254
 255   // Check if we are entering the EXIT block.
 256   if (Blk == &(L.getLocationContext()->getCFG()->getExit())) {
 257     assert(L.getLocationContext()->getCFG()->getExit().empty() &&
 258            "EXIT block cannot contain Stmts.");
 259
 260     // Get return statement..
 261     const ReturnStmt *RS = nullptr;
 262     if (!L.getSrc()->empty()) {
 263       CFGElement LastElement = L.getSrc()->back();
 264       if (std::optional<CFGStmt> LastStmt = LastElement.getAs<CFGStmt>()) {
 265         RS = dyn_cast<ReturnStmt>(LastStmt->getStmt());
 266       } else if (std::optional<CFGAutomaticObjDtor> AutoDtor =
 267                      LastElement.getAs<CFGAutomaticObjDtor>()) {
 268         RS = dyn_cast<ReturnStmt>(AutoDtor->getTriggerStmt());
 269       }
 270     }
 271
 272     // Process the final state transition.
 273     ExprEng.processEndOfFunction(BuilderCtx, Pred, RS);
 274
 275     // This path is done. Don't enqueue any more nodes.
 276     return;
 277   }
 278
 279   // Call into the ExprEngine to process entering the CFGBlock.
 280   ExplodedNodeSet dstNodes;
 281   BlockEntrance BE(Blk, Pred->getLocationContext());
 282   NodeBuilderWithSinks nodeBuilder(Pred, dstNodes, BuilderCtx, BE);
 283   ExprEng.processCFGBlockEntrance(L, nodeBuilder, Pred);
 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
 294 void CoreEngine::HandleBlockEntrance(const BlockEntrance &L,
 295                                        ExplodedNode *Pred) {
 296   // Increment the block counter.
 297   const LocationContext *LC = Pred->getLocationContext();
 298   unsigned BlockId = L.getBlock()->getBlockID();
 299   BlockCounter Counter = WList->getBlockCounter();
 300   Counter = BCounterFactory.IncrementCount(Counter, LC->getStackFrame(),
 301                                            BlockId);
 302   setBlockCounter(Counter);
 303
 304   // Process the entrance of the block.
 305   if (std::optional<CFGElement> E = L.getFirstElement()) {
 306     NodeBuilderContext Ctx(*this, L.getBlock(), Pred);
 307     ExprEng.processCFGElement(*E, Pred, 0, &Ctx);
 308   } else
 309     HandleBlockExit(L.getBlock(), Pred);
 310 }
 311
 312 void CoreEngine::HandleBlockExit(const CFGBlock * B, ExplodedNode *Pred) {
 313   if (const Stmt *Term = B->getTerminatorStmt()) {
 314     switch (Term->getStmtClass()) {
 315       default:
 316         llvm_unreachable("Analysis for this terminator not implemented.");
 317
 318       case Stmt::CXXBindTemporaryExprClass:
 319         HandleCleanupTemporaryBranch(
 320             cast<CXXBindTemporaryExpr>(Term), B, Pred);
 321         return;
 322
 323       // Model static initializers.
 324       case Stmt::DeclStmtClass:
 325         HandleStaticInit(cast<DeclStmt>(Term), B, Pred);
 326         return;
 327
 328       case Stmt::BinaryOperatorClass: // '&&' and '||'
 329         HandleBranch(cast<BinaryOperator>(Term)->getLHS(), Term, B, Pred);
 330         return;
 331
 332       case Stmt::BinaryConditionalOperatorClass:
 333       case Stmt::ConditionalOperatorClass:
 334         HandleBranch(cast<AbstractConditionalOperator>(Term)->getCond(),
 335                      Term, B, Pred);
 336         return;
 337
 338         // FIXME: Use constant-folding in CFG construction to simplify this
 339         // case.
 340
 341       case Stmt::ChooseExprClass:
 342         HandleBranch(cast<ChooseExpr>(Term)->getCond(), Term, B, Pred);
 343         return;
 344
 345       case Stmt::CXXTryStmtClass:
 346         // Generate a node for each of the successors.
 347         // Our logic for EH analysis can certainly be improved.
 348         for (CFGBlock::const_succ_iterator it = B->succ_begin(),
 349              et = B->succ_end(); it != et; ++it) {
 350           if (const CFGBlock *succ = *it) {
 351             generateNode(BlockEdge(B, succ, Pred->getLocationContext()),
 352                          Pred->State, Pred);
 353           }
 354         }
 355         return;
 356
 357       case Stmt::DoStmtClass:
 358         HandleBranch(cast<DoStmt>(Term)->getCond(), Term, B, Pred);
 359         return;
 360
 361       case Stmt::CXXForRangeStmtClass:
 362         HandleBranch(cast<CXXForRangeStmt>(Term)->getCond(), Term, B, Pred);
 363         return;
 364
 365       case Stmt::ForStmtClass:
 366         HandleBranch(cast<ForStmt>(Term)->getCond(), Term, B, Pred);
 367         return;
 368
 369       case Stmt::SEHLeaveStmtClass:
 370       case Stmt::ContinueStmtClass:
 371       case Stmt::BreakStmtClass:
 372       case Stmt::GotoStmtClass:
 373         break;
 374
 375       case Stmt::IfStmtClass:
 376         HandleBranch(cast<IfStmt>(Term)->getCond(), Term, B, Pred);
 377         return;
 378
 379       case Stmt::IndirectGotoStmtClass: {
 380         // Only 1 successor: the indirect goto dispatch block.
 381         assert(B->succ_size() == 1);
 382
 383         IndirectGotoNodeBuilder
 384            builder(Pred, B, cast<IndirectGotoStmt>(Term)->getTarget(),
 385                    *(B->succ_begin()), this);
 386
 387         ExprEng.processIndirectGoto(builder);
 388         return;
 389       }
 390
 391       case Stmt::ObjCForCollectionStmtClass:
 392         // In the case of ObjCForCollectionStmt, it appears twice in a CFG:
 393         //
 394         //  (1) inside a basic block, which represents the binding of the
 395         //      'element' variable to a value.
 396         //  (2) in a terminator, which represents the branch.
 397         //
 398         // For (1), ExprEngine will bind a value (i.e., 0 or 1) indicating
 399         // whether or not collection contains any more elements.  We cannot
 400         // just test to see if the element is nil because a container can
 401         // contain nil elements.
 402         HandleBranch(Term, Term, B, Pred);
 403         return;
 404
 405       case Stmt::SwitchStmtClass: {
 406         SwitchNodeBuilder builder(Pred, B, cast<SwitchStmt>(Term)->getCond(),
 407                                     this);
 408
 409         ExprEng.processSwitch(builder);
 410         return;
 411       }
 412
 413       case Stmt::WhileStmtClass:
 414         HandleBranch(cast<WhileStmt>(Term)->getCond(), Term, B, Pred);
 415         return;
 416
 417       case Stmt::GCCAsmStmtClass:
 418         assert(cast<GCCAsmStmt>(Term)->isAsmGoto() && "Encountered GCCAsmStmt without labels");
 419         // TODO: Handle jumping to labels
 420         return;
 421     }
 422   }
 423
 424   if (B->getTerminator().isVirtualBaseBranch()) {
 425     HandleVirtualBaseBranch(B, Pred);
 426     return;
 427   }
 428
 429   assert(B->succ_size() == 1 &&
 430          "Blocks with no terminator should have at most 1 successor.");
 431
 432   generateNode(BlockEdge(B, *(B->succ_begin()), Pred->getLocationContext()),
 433                Pred->State, Pred);
 434 }
 435
 436 void CoreEngine::HandleCallEnter(const CallEnter &CE, ExplodedNode *Pred) {
 437   NodeBuilderContext BuilderCtx(*this, CE.getEntry(), Pred);
 438   ExprEng.processCallEnter(BuilderCtx, CE, Pred);
 439 }
 440
 441 void CoreEngine::HandleBranch(const Stmt *Cond, const Stmt *Term,
 442                                 const CFGBlock * B, ExplodedNode *Pred) {
 443   assert(B->succ_size() == 2);
 444   NodeBuilderContext Ctx(*this, B, Pred);
 445   ExplodedNodeSet Dst;
 446   ExprEng.processBranch(Cond, Ctx, Pred, Dst, *(B->succ_begin()),
 447                        *(B->succ_begin() + 1));
 448   // Enqueue the new frontier onto the worklist.
 449   enqueue(Dst);
 450 }
 451
 452 void CoreEngine::HandleCleanupTemporaryBranch(const CXXBindTemporaryExpr *BTE,
 453                                               const CFGBlock *B,
 454                                               ExplodedNode *Pred) {
 455   assert(B->succ_size() == 2);
 456   NodeBuilderContext Ctx(*this, B, Pred);
 457   ExplodedNodeSet Dst;
 458   ExprEng.processCleanupTemporaryBranch(BTE, 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::HandleStaticInit(const DeclStmt *DS, const CFGBlock *B,
 465                                   ExplodedNode *Pred) {
 466   assert(B->succ_size() == 2);
 467   NodeBuilderContext Ctx(*this, B, Pred);
 468   ExplodedNodeSet Dst;
 469   ExprEng.processStaticInitializer(DS, Ctx, Pred, Dst,
 470                                   *(B->succ_begin()), *(B->succ_begin()+1));
 471   // Enqueue the new frontier onto the worklist.
 472   enqueue(Dst);
 473 }
 474
 475 void CoreEngine::HandlePostStmt(const CFGBlock *B, unsigned StmtIdx,
 476                                 ExplodedNode *Pred) {
 477   assert(B);
 478   assert(!B->empty());
 479
 480   if (StmtIdx == B->size())
 481     HandleBlockExit(B, Pred);
 482   else {
 483     NodeBuilderContext Ctx(*this, B, Pred);
 484     ExprEng.processCFGElement((*B)[StmtIdx], Pred, StmtIdx, &Ctx);
 485   }
 486 }
 487
 488 void CoreEngine::HandleVirtualBaseBranch(const CFGBlock *B,
 489                                          ExplodedNode *Pred) {
 490   const LocationContext *LCtx = Pred->getLocationContext();
 491   if (const auto *CallerCtor = dyn_cast_or_null<CXXConstructExpr>(
 492           LCtx->getStackFrame()->getCallSite())) {
 493     switch (CallerCtor->getConstructionKind()) {
 494     case CXXConstructionKind::NonVirtualBase:
 495     case CXXConstructionKind::VirtualBase: {
 496       BlockEdge Loc(B, *B->succ_begin(), LCtx);
 497       HandleBlockEdge(Loc, Pred);
 498       return;
 499     }
 500     default:
 501       break;
 502     }
 503   }
 504
 505   // We either don't see a parent stack frame because we're in the top frame,
 506   // or the parent stack frame doesn't initialize our virtual bases.
 507   BlockEdge Loc(B, *(B->succ_begin() + 1), LCtx);
 508   HandleBlockEdge(Loc, Pred);
 509 }
 510
 511 /// generateNode - Utility method to generate nodes, hook up successors,
 512 ///  and add nodes to the worklist.
 513 void CoreEngine::generateNode(const ProgramPoint &Loc,
 514                               ProgramStateRef State,
 515                               ExplodedNode *Pred) {
 516   bool IsNew;
 517   ExplodedNode *Node = G.getNode(Loc, State, false, &IsNew);
 518
 519   if (Pred)
 520     Node->addPredecessor(Pred, G); // Link 'Node' with its predecessor.
 521   else {
 522     assert(IsNew);
 523     G.addRoot(Node); // 'Node' has no predecessor.  Make it a root.
 524   }
 525
 526   // Only add 'Node' to the worklist if it was freshly generated.
 527   if (IsNew) WList->enqueue(Node);
 528 }
 529
 530 void CoreEngine::enqueueStmtNode(ExplodedNode *N,
 531                                  const CFGBlock *Block, unsigned Idx) {
 532   assert(Block);
 533   assert(!N->isSink());
 534
 535   // Check if this node entered a callee.
 536   if (N->getLocation().getAs<CallEnter>()) {
 537     // Still use the index of the CallExpr. It's needed to create the callee
 538     // StackFrameContext.
 539     WList->enqueue(N, Block, Idx);
 540     return;
 541   }
 542
 543   // Do not create extra nodes. Move to the next CFG element.
 544   if (N->getLocation().getAs<PostInitializer>() ||
 545       N->getLocation().getAs<PostImplicitCall>()||
 546       N->getLocation().getAs<LoopExit>()) {
 547     WList->enqueue(N, Block, Idx+1);
 548     return;
 549   }
 550
 551   if (N->getLocation().getAs<EpsilonPoint>()) {
 552     WList->enqueue(N, Block, Idx);
 553     return;
 554   }
 555
 556   if ((*Block)[Idx].getKind() == CFGElement::NewAllocator) {
 557     WList->enqueue(N, Block, Idx+1);
 558     return;
 559   }
 560
 561   // At this point, we know we're processing a normal statement.
 562   CFGStmt CS = (*Block)[Idx].castAs<CFGStmt>();
 563   PostStmt Loc(CS.getStmt(), N->getLocationContext());
 564
 565   if (Loc == N->getLocation().withTag(nullptr)) {
 566     // Note: 'N' should be a fresh node because otherwise it shouldn't be
 567     // a member of Deferred.
 568     WList->enqueue(N, Block, Idx+1);
 569     return;
 570   }
 571
 572   bool IsNew;
 573   ExplodedNode *Succ = G.getNode(Loc, N->getState(), false, &IsNew);
 574   Succ->addPredecessor(N, G);
 575
 576   if (IsNew)
 577     WList->enqueue(Succ, Block, Idx+1);
 578 }
 579
 580 ExplodedNode *CoreEngine::generateCallExitBeginNode(ExplodedNode *N,
 581                                                     const ReturnStmt *RS) {
 582   // Create a CallExitBegin node and enqueue it.
 583   const auto *LocCtx = cast<StackFrameContext>(N->getLocationContext());
 584
 585   // Use the callee location context.
 586   CallExitBegin Loc(LocCtx, RS);
 587
 588   bool isNew;
 589   ExplodedNode *Node = G.getNode(Loc, N->getState(), false, &isNew);
 590   Node->addPredecessor(N, G);
 591   return isNew ? Node : nullptr;
 592 }
 593
 594 void CoreEngine::enqueue(ExplodedNodeSet &Set) {
 595   for (const auto I : Set)
 596     WList->enqueue(I);
 597 }
 598
 599 void CoreEngine::enqueue(ExplodedNodeSet &Set,
 600                          const CFGBlock *Block, unsigned Idx) {
 601   for (const auto I : Set)
 602     enqueueStmtNode(I, Block, Idx);
 603 }
 604
 605 void CoreEngine::enqueueEndOfFunction(ExplodedNodeSet &Set, const ReturnStmt *RS) {
 606   for (auto *I : Set) {
 607     // If we are in an inlined call, generate CallExitBegin node.
 608     if (I->getLocationContext()->getParent()) {
 609       I = generateCallExitBeginNode(I, RS);
 610       if (I)
 611         WList->enqueue(I);
 612     } else {
 613       // TODO: We should run remove dead bindings here.
 614       G.addEndOfPath(I);
 615       NumPathsExplored++;
 616     }
 617   }
 618 }
 619
 620 void NodeBuilder::anchor() {}
 621
 622 ExplodedNode* NodeBuilder::generateNodeImpl(const ProgramPoint &Loc,
 623                                             ProgramStateRef State,
 624                                             ExplodedNode *FromN,
 625                                             bool MarkAsSink) {
 626   HasGeneratedNodes = true;
 627   bool IsNew;
 628   ExplodedNode *N = C.getEngine().G.getNode(Loc, State, MarkAsSink, &IsNew);
 629   N->addPredecessor(FromN, C.getEngine().G);
 630   Frontier.erase(FromN);
 631
 632   if (!IsNew)
 633     return nullptr;
 634
 635   if (!MarkAsSink)
 636     Frontier.Add(N);
 637
 638   return N;
 639 }
 640
 641 void NodeBuilderWithSinks::anchor() {}
 642
 643 StmtNodeBuilder::~StmtNodeBuilder() {
 644   if (EnclosingBldr)
 645     for (const auto I : Frontier)
 646       EnclosingBldr->addNodes(I);
 647 }
 648
 649 void BranchNodeBuilder::anchor() {}
 650
 651 ExplodedNode *BranchNodeBuilder::generateNode(ProgramStateRef State,
 652                                               bool Branch,
 653                                               ExplodedNode *NodePred) {
 654   const CFGBlock *Dst = Branch ? DstT : DstF;
 655
 656   if (!Dst)
 657     return nullptr;
 658
 659   ProgramPoint Loc =
 660       BlockEdge(C.getBlock(), Dst, NodePred->getLocationContext());
 661   ExplodedNode *Succ = generateNodeImpl(Loc, State, NodePred);
 662   return Succ;
 663 }
 664
 665 ExplodedNode*
 666 IndirectGotoNodeBuilder::generateNode(const iterator &I,
 667                                       ProgramStateRef St,
 668                                       bool IsSink) {
 669   bool IsNew;
 670   ExplodedNode *Succ =
 671       Eng.G.getNode(BlockEdge(Src, I.getBlock(), Pred->getLocationContext()),
 672                     St, IsSink, &IsNew);
 673   Succ->addPredecessor(Pred, Eng.G);
 674
 675   if (!IsNew)
 676     return nullptr;
 677
 678   if (!IsSink)
 679     Eng.WList->enqueue(Succ);
 680
 681   return Succ;
 682 }
 683
 684 ExplodedNode*
 685 SwitchNodeBuilder::generateCaseStmtNode(const iterator &I,
 686                                         ProgramStateRef St) {
 687   bool IsNew;
 688   ExplodedNode *Succ =
 689       Eng.G.getNode(BlockEdge(Src, I.getBlock(), Pred->getLocationContext()),
 690                     St, false, &IsNew);
 691   Succ->addPredecessor(Pred, Eng.G);
 692   if (!IsNew)
 693     return nullptr;
 694
 695   Eng.WList->enqueue(Succ);
 696   return Succ;
 697 }
 698
 699 ExplodedNode*
 700 SwitchNodeBuilder::generateDefaultCaseNode(ProgramStateRef St,
 701                                            bool IsSink) {
 702   // Get the block for the default case.
 703   assert(Src->succ_rbegin() != Src->succ_rend());
 704   CFGBlock *DefaultBlock = *Src->succ_rbegin();
 705
 706   // Basic correctness check for default blocks that are unreachable and not
 707   // caught by earlier stages.
 708   if (!DefaultBlock)
 709     return nullptr;
 710
 711   bool IsNew;
 712   ExplodedNode *Succ =
 713       Eng.G.getNode(BlockEdge(Src, DefaultBlock, Pred->getLocationContext()),
 714                     St, IsSink, &IsNew);
 715   Succ->addPredecessor(Pred, Eng.G);
 716
 717   if (!IsNew)
 718     return nullptr;
 719
 720   if (!IsSink)
 721     Eng.WList->enqueue(Succ);
 722
 723   return Succ;
 724 }