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llvm-project/clang/lib/StaticAnalyzer/Core/CoreEngine.cpp

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//===- CoreEngine.cpp - Path-Sensitive Dataflow Engine --------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines a generic engine for intraprocedural, path-sensitive,
// dataflow analysis via graph reachability engine.
//
//===----------------------------------------------------------------------===//
#include "clang/StaticAnalyzer/Core/PathSensitive/CoreEngine.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/Stmt.h"
#include "clang/AST/StmtCXX.h"
#include "clang/Analysis/AnalysisDeclContext.h"
#include "clang/Analysis/CFG.h"
#include "clang/Analysis/ProgramPoint.h"
#include "clang/Basic/LLVM.h"
#include "clang/StaticAnalyzer/Core/AnalyzerOptions.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/BlockCounter.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/FunctionSummary.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/WorkList.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include <algorithm>
#include <cassert>
#include <memory>
#include <utility>
using namespace clang;
using namespace ento;
#define DEBUG_TYPE "CoreEngine"
STATISTIC(NumSteps,
"The # of steps executed.");
STATISTIC(NumReachedMaxSteps,
"The # of times we reached the max number of steps.");
STATISTIC(NumPathsExplored,
"The # of paths explored by the analyzer.");
//===----------------------------------------------------------------------===//
// Core analysis engine.
//===----------------------------------------------------------------------===//
static std::unique_ptr<WorkList> generateWorkList(AnalyzerOptions &Opts) {
switch (Opts.getExplorationStrategy()) {
case ExplorationStrategyKind::DFS:
return WorkList::makeDFS();
case ExplorationStrategyKind::BFS:
return WorkList::makeBFS();
case ExplorationStrategyKind::BFSBlockDFSContents:
return WorkList::makeBFSBlockDFSContents();
case ExplorationStrategyKind::UnexploredFirst:
return WorkList::makeUnexploredFirst();
case ExplorationStrategyKind::UnexploredFirstQueue:
return WorkList::makeUnexploredFirstPriorityQueue();
case ExplorationStrategyKind::UnexploredFirstLocationQueue:
return WorkList::makeUnexploredFirstPriorityLocationQueue();
}
llvm_unreachable("Unknown AnalyzerOptions::ExplorationStrategyKind");
}
CoreEngine::CoreEngine(ExprEngine &exprengine, FunctionSummariesTy *FS,
AnalyzerOptions &Opts)
: ExprEng(exprengine), WList(generateWorkList(Opts)),
BCounterFactory(G.getAllocator()), FunctionSummaries(FS) {}
/// ExecuteWorkList - Run the worklist algorithm for a maximum number of steps.
bool CoreEngine::ExecuteWorkList(const LocationContext *L, unsigned Steps,
ProgramStateRef InitState) {
if (G.num_roots() == 0) { // Initialize the analysis by constructing
// the root if none exists.
const CFGBlock *Entry = &(L->getCFG()->getEntry());
assert(Entry->empty() && "Entry block must be empty.");
assert(Entry->succ_size() == 1 && "Entry block must have 1 successor.");
// Mark the entry block as visited.
FunctionSummaries->markVisitedBasicBlock(Entry->getBlockID(),
L->getDecl(),
L->getCFG()->getNumBlockIDs());
// Get the solitary successor.
const CFGBlock *Succ = *(Entry->succ_begin());
// Construct an edge representing the
// starting location in the function.
BlockEdge StartLoc(Entry, Succ, L);
// Set the current block counter to being empty.
WList->setBlockCounter(BCounterFactory.GetEmptyCounter());
if (!InitState)
InitState = ExprEng.getInitialState(L);
bool IsNew;
ExplodedNode *Node = G.getNode(StartLoc, InitState, false, &IsNew);
assert(IsNew);
G.addRoot(Node);
NodeBuilderContext BuilderCtx(*this, StartLoc.getDst(), Node);
ExplodedNodeSet DstBegin;
ExprEng.processBeginOfFunction(BuilderCtx, Node, DstBegin, StartLoc);
enqueue(DstBegin);
}
// Check if we have a steps limit
bool UnlimitedSteps = Steps == 0;
// Cap our pre-reservation in the event that the user specifies
// a very large number of maximum steps.
const unsigned PreReservationCap = 4000000;
if(!UnlimitedSteps)
G.reserve(std::min(Steps,PreReservationCap));
while (WList->hasWork()) {
if (!UnlimitedSteps) {
if (Steps == 0) {
NumReachedMaxSteps++;
break;
}
--Steps;
}
NumSteps++;
const WorkListUnit& WU = WList->dequeue();
// Set the current block counter.
WList->setBlockCounter(WU.getBlockCounter());
// Retrieve the node.
ExplodedNode *Node = WU.getNode();
dispatchWorkItem(Node, Node->getLocation(), WU);
}
ExprEng.processEndWorklist();
return WList->hasWork();
}
void CoreEngine::dispatchWorkItem(ExplodedNode* Pred, ProgramPoint Loc,
const WorkListUnit& WU) {
// Dispatch on the location type.
switch (Loc.getKind()) {
case ProgramPoint::BlockEdgeKind:
HandleBlockEdge(Loc.castAs<BlockEdge>(), Pred);
break;
case ProgramPoint::BlockEntranceKind:
HandleBlockEntrance(Loc.castAs<BlockEntrance>(), Pred);
break;
case ProgramPoint::BlockExitKind:
assert(false && "BlockExit location never occur in forward analysis.");
break;
case ProgramPoint::CallEnterKind:
HandleCallEnter(Loc.castAs<CallEnter>(), Pred);
break;
case ProgramPoint::CallExitBeginKind:
ExprEng.processCallExit(Pred);
break;
case ProgramPoint::EpsilonKind: {
assert(Pred->hasSinglePred() &&
"Assume epsilon has exactly one predecessor by construction");
ExplodedNode *PNode = Pred->getFirstPred();
dispatchWorkItem(Pred, PNode->getLocation(), WU);
break;
}
default:
assert(Loc.getAs<PostStmt>() ||
Loc.getAs<PostInitializer>() ||
Loc.getAs<PostImplicitCall>() ||
Loc.getAs<CallExitEnd>() ||
Loc.getAs<LoopExit>() ||
Loc.getAs<PostAllocatorCall>());
HandlePostStmt(WU.getBlock(), WU.getIndex(), Pred);
break;
}
}
bool CoreEngine::ExecuteWorkListWithInitialState(const LocationContext *L,
unsigned Steps,
ProgramStateRef InitState,
ExplodedNodeSet &Dst) {
bool DidNotFinish = ExecuteWorkList(L, Steps, InitState);
for (ExplodedGraph::eop_iterator I = G.eop_begin(), E = G.eop_end(); I != E;
++I) {
Dst.Add(*I);
}
return DidNotFinish;
}
void CoreEngine::HandleBlockEdge(const BlockEdge &L, ExplodedNode *Pred) {
const CFGBlock *Blk = L.getDst();
NodeBuilderContext BuilderCtx(*this, Blk, Pred);
// Mark this block as visited.
const LocationContext *LC = Pred->getLocationContext();
FunctionSummaries->markVisitedBasicBlock(Blk->getBlockID(),
LC->getDecl(),
LC->getCFG()->getNumBlockIDs());
// Display a prunable path note to the user if it's a virtual bases branch
// and we're taking the path that skips virtual base constructors.
if (L.getSrc()->getTerminator().isVirtualBaseBranch() &&
L.getDst() == *L.getSrc()->succ_begin()) {
ProgramPoint P = L.withTag(getDataTags().make<NoteTag>(
[](BugReporterContext &, PathSensitiveBugReport &) -> std::string {
// TODO: Just call out the name of the most derived class
// when we know it.
return "Virtual base initialization skipped because "
"it has already been handled by the most derived class";
},
/*IsPrunable=*/true));
// Perform the transition.
ExplodedNodeSet Dst;
NodeBuilder Bldr(Pred, Dst, BuilderCtx);
Pred = Bldr.generateNode(P, Pred->getState(), Pred);
if (!Pred)
return;
}
// Check if we are entering the EXIT block.
if (Blk == &(L.getLocationContext()->getCFG()->getExit())) {
assert(L.getLocationContext()->getCFG()->getExit().empty() &&
"EXIT block cannot contain Stmts.");
// Get return statement..
const ReturnStmt *RS = nullptr;
if (!L.getSrc()->empty()) {
CFGElement LastElement = L.getSrc()->back();
if (Optional<CFGStmt> LastStmt = LastElement.getAs<CFGStmt>()) {
RS = dyn_cast<ReturnStmt>(LastStmt->getStmt());
} else if (Optional<CFGAutomaticObjDtor> AutoDtor =
LastElement.getAs<CFGAutomaticObjDtor>()) {
RS = dyn_cast<ReturnStmt>(AutoDtor->getTriggerStmt());
}
}
// Process the final state transition.
ExprEng.processEndOfFunction(BuilderCtx, Pred, RS);
// This path is done. Don't enqueue any more nodes.
return;
}
// Call into the ExprEngine to process entering the CFGBlock.
ExplodedNodeSet dstNodes;
BlockEntrance BE(Blk, Pred->getLocationContext());
NodeBuilderWithSinks nodeBuilder(Pred, dstNodes, BuilderCtx, BE);
ExprEng.processCFGBlockEntrance(L, nodeBuilder, Pred);
// Auto-generate a node.
if (!nodeBuilder.hasGeneratedNodes()) {
nodeBuilder.generateNode(Pred->State, Pred);
}
// Enqueue nodes onto the worklist.
enqueue(dstNodes);
}
void CoreEngine::HandleBlockEntrance(const BlockEntrance &L,
ExplodedNode *Pred) {
// Increment the block counter.
const LocationContext *LC = Pred->getLocationContext();
unsigned BlockId = L.getBlock()->getBlockID();
BlockCounter Counter = WList->getBlockCounter();
Counter = BCounterFactory.IncrementCount(Counter, LC->getStackFrame(),
BlockId);
WList->setBlockCounter(Counter);
// Process the entrance of the block.
if (Optional<CFGElement> E = L.getFirstElement()) {
NodeBuilderContext Ctx(*this, L.getBlock(), Pred);
ExprEng.processCFGElement(*E, Pred, 0, &Ctx);
}
else
HandleBlockExit(L.getBlock(), Pred);
}
void CoreEngine::HandleBlockExit(const CFGBlock * B, ExplodedNode *Pred) {
if (const Stmt *Term = B->getTerminatorStmt()) {
switch (Term->getStmtClass()) {
default:
llvm_unreachable("Analysis for this terminator not implemented.");
case Stmt::CXXBindTemporaryExprClass:
HandleCleanupTemporaryBranch(
cast<CXXBindTemporaryExpr>(Term), B, Pred);
return;
// Model static initializers.
case Stmt::DeclStmtClass:
HandleStaticInit(cast<DeclStmt>(Term), B, Pred);
return;
case Stmt::BinaryOperatorClass: // '&&' and '||'
HandleBranch(cast<BinaryOperator>(Term)->getLHS(), Term, B, Pred);
return;
case Stmt::BinaryConditionalOperatorClass:
case Stmt::ConditionalOperatorClass:
HandleBranch(cast<AbstractConditionalOperator>(Term)->getCond(),
Term, B, Pred);
return;
// FIXME: Use constant-folding in CFG construction to simplify this
// case.
case Stmt::ChooseExprClass:
HandleBranch(cast<ChooseExpr>(Term)->getCond(), Term, B, Pred);
return;
case Stmt::CXXTryStmtClass:
// Generate a node for each of the successors.
// Our logic for EH analysis can certainly be improved.
for (CFGBlock::const_succ_iterator it = B->succ_begin(),
et = B->succ_end(); it != et; ++it) {
if (const CFGBlock *succ = *it) {
generateNode(BlockEdge(B, succ, Pred->getLocationContext()),
Pred->State, Pred);
}
}
return;
case Stmt::DoStmtClass:
HandleBranch(cast<DoStmt>(Term)->getCond(), Term, B, Pred);
return;
case Stmt::CXXForRangeStmtClass:
HandleBranch(cast<CXXForRangeStmt>(Term)->getCond(), Term, B, Pred);
return;
case Stmt::ForStmtClass:
HandleBranch(cast<ForStmt>(Term)->getCond(), Term, B, Pred);
return;
case Stmt::SEHLeaveStmtClass:
case Stmt::ContinueStmtClass:
case Stmt::BreakStmtClass:
case Stmt::GotoStmtClass:
break;
case Stmt::IfStmtClass:
HandleBranch(cast<IfStmt>(Term)->getCond(), Term, B, Pred);
return;
case Stmt::IndirectGotoStmtClass: {
// Only 1 successor: the indirect goto dispatch block.
assert(B->succ_size() == 1);
IndirectGotoNodeBuilder
builder(Pred, B, cast<IndirectGotoStmt>(Term)->getTarget(),
*(B->succ_begin()), this);
ExprEng.processIndirectGoto(builder);
return;
}
case Stmt::ObjCForCollectionStmtClass:
// In the case of ObjCForCollectionStmt, it appears twice in a CFG:
//
// (1) inside a basic block, which represents the binding of the
// 'element' variable to a value.
// (2) in a terminator, which represents the branch.
//
// For (1), ExprEngine will bind a value (i.e., 0 or 1) indicating
// whether or not collection contains any more elements. We cannot
// just test to see if the element is nil because a container can
// contain nil elements.
HandleBranch(Term, Term, B, Pred);
return;
case Stmt::SwitchStmtClass: {
SwitchNodeBuilder builder(Pred, B, cast<SwitchStmt>(Term)->getCond(),
this);
ExprEng.processSwitch(builder);
return;
}
case Stmt::WhileStmtClass:
HandleBranch(cast<WhileStmt>(Term)->getCond(), Term, B, Pred);
return;
case Stmt::GCCAsmStmtClass:
assert(cast<GCCAsmStmt>(Term)->isAsmGoto() && "Encountered GCCAsmStmt without labels");
// TODO: Handle jumping to labels
return;
}
}
if (B->getTerminator().isVirtualBaseBranch()) {
HandleVirtualBaseBranch(B, Pred);
return;
}
assert(B->succ_size() == 1 &&
"Blocks with no terminator should have at most 1 successor.");
generateNode(BlockEdge(B, *(B->succ_begin()), Pred->getLocationContext()),
Pred->State, Pred);
}
void CoreEngine::HandleCallEnter(const CallEnter &CE, ExplodedNode *Pred) {
NodeBuilderContext BuilderCtx(*this, CE.getEntry(), Pred);
ExprEng.processCallEnter(BuilderCtx, CE, Pred);
}
void CoreEngine::HandleBranch(const Stmt *Cond, const Stmt *Term,
const CFGBlock * B, ExplodedNode *Pred) {
assert(B->succ_size() == 2);
NodeBuilderContext Ctx(*this, B, Pred);
ExplodedNodeSet Dst;
ExprEng.processBranch(Cond, Ctx, Pred, Dst, *(B->succ_begin()),
*(B->succ_begin() + 1));
// Enqueue the new frontier onto the worklist.
enqueue(Dst);
}
void CoreEngine::HandleCleanupTemporaryBranch(const CXXBindTemporaryExpr *BTE,
const CFGBlock *B,
ExplodedNode *Pred) {
assert(B->succ_size() == 2);
NodeBuilderContext Ctx(*this, B, Pred);
ExplodedNodeSet Dst;
ExprEng.processCleanupTemporaryBranch(BTE, Ctx, Pred, Dst, *(B->succ_begin()),
*(B->succ_begin() + 1));
// Enqueue the new frontier onto the worklist.
enqueue(Dst);
}
void CoreEngine::HandleStaticInit(const DeclStmt *DS, const CFGBlock *B,
ExplodedNode *Pred) {
assert(B->succ_size() == 2);
NodeBuilderContext Ctx(*this, B, Pred);
ExplodedNodeSet Dst;
ExprEng.processStaticInitializer(DS, Ctx, Pred, Dst,
*(B->succ_begin()), *(B->succ_begin()+1));
// Enqueue the new frontier onto the worklist.
enqueue(Dst);
}
void CoreEngine::HandlePostStmt(const CFGBlock *B, unsigned StmtIdx,
ExplodedNode *Pred) {
assert(B);
assert(!B->empty());
if (StmtIdx == B->size())
HandleBlockExit(B, Pred);
else {
NodeBuilderContext Ctx(*this, B, Pred);
ExprEng.processCFGElement((*B)[StmtIdx], Pred, StmtIdx, &Ctx);
}
}
void CoreEngine::HandleVirtualBaseBranch(const CFGBlock *B,
ExplodedNode *Pred) {
const LocationContext *LCtx = Pred->getLocationContext();
if (const auto *CallerCtor = dyn_cast_or_null<CXXConstructExpr>(
LCtx->getStackFrame()->getCallSite())) {
switch (CallerCtor->getConstructionKind()) {
case CXXConstructExpr::CK_NonVirtualBase:
case CXXConstructExpr::CK_VirtualBase: {
BlockEdge Loc(B, *B->succ_begin(), LCtx);
HandleBlockEdge(Loc, Pred);
return;
}
default:
break;
}
}
// We either don't see a parent stack frame because we're in the top frame,
// or the parent stack frame doesn't initialize our virtual bases.
BlockEdge Loc(B, *(B->succ_begin() + 1), LCtx);
HandleBlockEdge(Loc, Pred);
}
/// generateNode - Utility method to generate nodes, hook up successors,
/// and add nodes to the worklist.
void CoreEngine::generateNode(const ProgramPoint &Loc,
ProgramStateRef State,
ExplodedNode *Pred) {
bool IsNew;
ExplodedNode *Node = G.getNode(Loc, State, false, &IsNew);
if (Pred)
Node->addPredecessor(Pred, G); // Link 'Node' with its predecessor.
else {
assert(IsNew);
G.addRoot(Node); // 'Node' has no predecessor. Make it a root.
}
// Only add 'Node' to the worklist if it was freshly generated.
if (IsNew) WList->enqueue(Node);
}
void CoreEngine::enqueueStmtNode(ExplodedNode *N,
const CFGBlock *Block, unsigned Idx) {
assert(Block);
assert(!N->isSink());
// Check if this node entered a callee.
if (N->getLocation().getAs<CallEnter>()) {
// Still use the index of the CallExpr. It's needed to create the callee
// StackFrameContext.
WList->enqueue(N, Block, Idx);
return;
}
// Do not create extra nodes. Move to the next CFG element.
if (N->getLocation().getAs<PostInitializer>() ||
N->getLocation().getAs<PostImplicitCall>()||
N->getLocation().getAs<LoopExit>()) {
WList->enqueue(N, Block, Idx+1);
return;
}
if (N->getLocation().getAs<EpsilonPoint>()) {
WList->enqueue(N, Block, Idx);
return;
}
if ((*Block)[Idx].getKind() == CFGElement::NewAllocator) {
WList->enqueue(N, Block, Idx+1);
return;
}
// At this point, we know we're processing a normal statement.
CFGStmt CS = (*Block)[Idx].castAs<CFGStmt>();
PostStmt Loc(CS.getStmt(), N->getLocationContext());
if (Loc == N->getLocation().withTag(nullptr)) {
// Note: 'N' should be a fresh node because otherwise it shouldn't be
// a member of Deferred.
WList->enqueue(N, Block, Idx+1);
return;
}
bool IsNew;
ExplodedNode *Succ = G.getNode(Loc, N->getState(), false, &IsNew);
Succ->addPredecessor(N, G);
if (IsNew)
WList->enqueue(Succ, Block, Idx+1);
}
ExplodedNode *CoreEngine::generateCallExitBeginNode(ExplodedNode *N,
const ReturnStmt *RS) {
// Create a CallExitBegin node and enqueue it.
const auto *LocCtx = cast<StackFrameContext>(N->getLocationContext());
// Use the callee location context.
CallExitBegin Loc(LocCtx, RS);
bool isNew;
ExplodedNode *Node = G.getNode(Loc, N->getState(), false, &isNew);
Node->addPredecessor(N, G);
return isNew ? Node : nullptr;
}
void CoreEngine::enqueue(ExplodedNodeSet &Set) {
for (const auto I : Set)
WList->enqueue(I);
}
void CoreEngine::enqueue(ExplodedNodeSet &Set,
const CFGBlock *Block, unsigned Idx) {
for (const auto I : Set)
enqueueStmtNode(I, Block, Idx);
}
void CoreEngine::enqueueEndOfFunction(ExplodedNodeSet &Set, const ReturnStmt *RS) {
for (auto I : Set) {
// If we are in an inlined call, generate CallExitBegin node.
if (I->getLocationContext()->getParent()) {
I = generateCallExitBeginNode(I, RS);
if (I)
WList->enqueue(I);
} else {
// TODO: We should run remove dead bindings here.
G.addEndOfPath(I);
NumPathsExplored++;
}
}
}
void NodeBuilder::anchor() {}
ExplodedNode* NodeBuilder::generateNodeImpl(const ProgramPoint &Loc,
ProgramStateRef State,
ExplodedNode *FromN,
bool MarkAsSink) {
HasGeneratedNodes = true;
bool IsNew;
ExplodedNode *N = C.Eng.G.getNode(Loc, State, MarkAsSink, &IsNew);
N->addPredecessor(FromN, C.Eng.G);
Frontier.erase(FromN);
if (!IsNew)
return nullptr;
if (!MarkAsSink)
Frontier.Add(N);
return N;
}
void NodeBuilderWithSinks::anchor() {}
StmtNodeBuilder::~StmtNodeBuilder() {
if (EnclosingBldr)
for (const auto I : Frontier)
EnclosingBldr->addNodes(I);
}
void BranchNodeBuilder::anchor() {}
ExplodedNode *BranchNodeBuilder::generateNode(ProgramStateRef State,
bool branch,
ExplodedNode *NodePred) {
// If the branch has been marked infeasible we should not generate a node.
if (!isFeasible(branch))
return nullptr;
ProgramPoint Loc = BlockEdge(C.Block, branch ? DstT:DstF,
NodePred->getLocationContext());
ExplodedNode *Succ = generateNodeImpl(Loc, State, NodePred);
return Succ;
}
ExplodedNode*
IndirectGotoNodeBuilder::generateNode(const iterator &I,
ProgramStateRef St,
bool IsSink) {
bool IsNew;
ExplodedNode *Succ =
Eng.G.getNode(BlockEdge(Src, I.getBlock(), Pred->getLocationContext()),
St, IsSink, &IsNew);
Succ->addPredecessor(Pred, Eng.G);
if (!IsNew)
return nullptr;
if (!IsSink)
Eng.WList->enqueue(Succ);
return Succ;
}
ExplodedNode*
SwitchNodeBuilder::generateCaseStmtNode(const iterator &I,
ProgramStateRef St) {
bool IsNew;
ExplodedNode *Succ =
Eng.G.getNode(BlockEdge(Src, I.getBlock(), Pred->getLocationContext()),
St, false, &IsNew);
Succ->addPredecessor(Pred, Eng.G);
if (!IsNew)
return nullptr;
Eng.WList->enqueue(Succ);
return Succ;
}
ExplodedNode*
SwitchNodeBuilder::generateDefaultCaseNode(ProgramStateRef St,
bool IsSink) {
// Get the block for the default case.
assert(Src->succ_rbegin() != Src->succ_rend());
CFGBlock *DefaultBlock = *Src->succ_rbegin();
// Sanity check for default blocks that are unreachable and not caught
// by earlier stages.
if (!DefaultBlock)
return nullptr;
bool IsNew;
ExplodedNode *Succ =
Eng.G.getNode(BlockEdge(Src, DefaultBlock, Pred->getLocationContext()),
St, IsSink, &IsNew);
Succ->addPredecessor(Pred, Eng.G);
if (!IsNew)
return nullptr;
if (!IsSink)
Eng.WList->enqueue(Succ);
return Succ;
}
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