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//===- CoreEngine.h - Path-Sensitive Dataflow Engine ------------*- C++ -*-===//

//

// 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.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_COREENGINE_H

#define LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_COREENGINE_H

#include "clang/AST/Stmt.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/BugReporter/BugReporter.h"

#include "clang/StaticAnalyzer/Core/PathSensitive/BlockCounter.h"

#include "clang/StaticAnalyzer/Core/PathSensitive/ExplodedGraph.h"

#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState_Fwd.h"

#include "clang/StaticAnalyzer/Core/PathSensitive/WorkList.h"

#include "llvm/ADT/SmallVector.h"

#include "llvm/Support/Casting.h"

#include <cassert>

#include <memory>

#include <utility>

#include <vector>

namespace clang {

class AnalyzerOptions;

class CXXBindTemporaryExpr;

class Expr;

class LabelDecl;

namespace ento {

class FunctionSummariesTy;

class ExprEngine;

//===----------------------------------------------------------------------===//

/// CoreEngine - Implements the core logic of the graph-reachability

///   analysis. It traverses the CFG and generates the ExplodedGraph.

///   Program "states" are treated as opaque void pointers.

///   The template class CoreEngine (which subclasses CoreEngine)

///   provides the matching component to the engine that knows the actual types

///   for states.  Note that this engine only dispatches to transfer functions

///   at the statement and block-level.  The analyses themselves must implement

///   any transfer function logic and the sub-expression level (if any).

class CoreEngine {

  friend class CommonNodeBuilder;

  friend class EndOfFunctionNodeBuilder;

  friend class ExprEngine;

  friend class IndirectGotoNodeBuilder;

  friend class NodeBuilder;

  friend struct NodeBuilderContext;

  friend class SwitchNodeBuilder;

public:

  using BlocksExhausted =

      std::vector<std::pair<BlockEdge, const ExplodedNode *>>;

  using BlocksAborted =

      std::vector<std::pair<const CFGBlock *, const ExplodedNode *>>;

private:

  ExprEngine &ExprEng;

  /// G - The simulation graph.  Each node is a (location,state) pair.

  mutable ExplodedGraph G;

  /// WList - A set of queued nodes that need to be processed by the

  ///  worklist algorithm.  It is up to the implementation of WList to decide

  ///  the order that nodes are processed.

  std::unique_ptr<WorkList> WList;

  std::unique_ptr<WorkList> CTUWList;

  /// BCounterFactory - A factory object for created BlockCounter objects.

  ///   These are used to record for key nodes in the ExplodedGraph the

  ///   number of times different CFGBlocks have been visited along a path.

  BlockCounter::Factory BCounterFactory;

  /// The locations where we stopped doing work because we visited a location

  ///  too many times.

  BlocksExhausted blocksExhausted;

  /// The locations where we stopped because the engine aborted analysis,

  /// usually because it could not reason about something.

  BlocksAborted blocksAborted;

  /// The information about functions shared by the whole translation unit.

  /// (This data is owned by AnalysisConsumer.)

  FunctionSummariesTy *FunctionSummaries;

  /// Add path tags with some useful data along the path when we see that

  /// something interesting is happening. This field is the allocator for such

  /// tags.

  DataTag::Factory DataTags;

  void setBlockCounter(BlockCounter C);

  void generateNode(const ProgramPoint &Loc,

                    ProgramStateRef State,

                    ExplodedNode *Pred);

  void HandleBlockEdge(const BlockEdge &E, ExplodedNode *Pred);

  void HandleBlockEntrance(const BlockEntrance &E, ExplodedNode *Pred);

  void HandleBlockExit(const CFGBlock *B, ExplodedNode *Pred);

  void HandleCallEnter(const CallEnter &CE, ExplodedNode *Pred);

  void HandlePostStmt(const CFGBlock *B, unsigned StmtIdx, ExplodedNode *Pred);

  void HandleBranch(const Stmt *Cond, const Stmt *Term, const CFGBlock *B,

                    ExplodedNode *Pred);

  void HandleCleanupTemporaryBranch(const CXXBindTemporaryExpr *BTE,

                                    const CFGBlock *B, ExplodedNode *Pred);

  /// Handle conditional logic for running static initializers.

  void HandleStaticInit(const DeclStmt *DS, const CFGBlock *B,

                        ExplodedNode *Pred);

  void HandleVirtualBaseBranch(const CFGBlock *B, ExplodedNode *Pred);

private:

  ExplodedNode *generateCallExitBeginNode(ExplodedNode *N,

                                          const ReturnStmt *RS);

public:

  /// Construct a CoreEngine object to analyze the provided CFG.

  CoreEngine(ExprEngine &exprengine,

             FunctionSummariesTy *FS,

             AnalyzerOptions &Opts);

  CoreEngine(const CoreEngine &) = delete;

  CoreEngine &operator=(const CoreEngine &) = delete;

  /// getGraph - Returns the exploded graph.

  ExplodedGraph &getGraph() { return G; }

  /// ExecuteWorkList - Run the worklist algorithm for a maximum number of

  ///  steps.  Returns true if there is still simulation state on the worklist.

  bool ExecuteWorkList(const LocationContext *L, unsigned Steps,

                       ProgramStateRef InitState);

  /// Returns true if there is still simulation state on the worklist.

  bool ExecuteWorkListWithInitialState(const LocationContext *L,

                                       unsigned Steps,

                                       ProgramStateRef InitState,

                                       ExplodedNodeSet &Dst);

  /// Dispatch the work list item based on the given location information.

  /// Use Pred parameter as the predecessor state.

  void dispatchWorkItem(ExplodedNode* Pred, ProgramPoint Loc,

                        const WorkListUnit& WU);

  // Functions for external checking of whether we have unfinished work

  bool wasBlockAborted() const { return !blocksAborted.empty(); }

  bool wasBlocksExhausted() const { return !blocksExhausted.empty(); }

  bool hasWorkRemaining() const { return wasBlocksExhausted() ||

                                         WList->hasWork() ||

                                         wasBlockAborted(); }

  /// Inform the CoreEngine that a basic block was aborted because

  /// it could not be completely analyzed.

  void addAbortedBlock(const ExplodedNode *node, const CFGBlock *block) {

    blocksAborted.push_back(std::make_pair(block, node));

  }

  WorkList *getWorkList() const { return WList.get(); }

  WorkList *getCTUWorkList() const { return CTUWList.get(); }

  BlocksExhausted::const_iterator blocks_exhausted_begin() const {

    return blocksExhausted.begin();

  }

  BlocksExhausted::const_iterator blocks_exhausted_end() const {

    return blocksExhausted.end();

  }

  BlocksAborted::const_iterator blocks_aborted_begin() const {

    return blocksAborted.begin();

  }

  BlocksAborted::const_iterator blocks_aborted_end() const {

    return blocksAborted.end();

  }

  /// Enqueue the given set of nodes onto the work list.

  void enqueue(ExplodedNodeSet &Set);

  /// Enqueue nodes that were created as a result of processing

  /// a statement onto the work list.

  void enqueue(ExplodedNodeSet &Set, const CFGBlock *Block, unsigned Idx);

  /// enqueue the nodes corresponding to the end of function onto the

  /// end of path / work list.

  void enqueueEndOfFunction(ExplodedNodeSet &Set, const ReturnStmt *RS);

  /// Enqueue a single node created as a result of statement processing.

  void enqueueStmtNode(ExplodedNode *N, const CFGBlock *Block, unsigned Idx);

  DataTag::Factory &getDataTags() { return DataTags; }

};

// TODO: Turn into a class.

struct NodeBuilderContext {

  const CoreEngine &Eng;

  const CFGBlock *Block;

  const LocationContext *LC;

  NodeBuilderContext(const CoreEngine &E, const CFGBlock *B,

                     const LocationContext *L)

      : Eng(E), Block(B), LC(L) {

    assert(B);

  }

  NodeBuilderContext(const CoreEngine &E, const CFGBlock *B, ExplodedNode *N)

      : NodeBuilderContext(E, B, N->getLocationContext()) {}

  /// Return the CFGBlock associated with this builder.

  const CFGBlock *getBlock() const { return Block; }

  /// Returns the number of times the current basic block has been

  /// visited on the exploded graph path.

  unsigned blockCount() const {

    return Eng.WList->getBlockCounter().getNumVisited(

                    LC->getStackFrame(),

                    Block->getBlockID());

  }

};

/// \class NodeBuilder

/// This is the simplest builder which generates nodes in the

/// ExplodedGraph.

///

/// The main benefit of the builder is that it automatically tracks the

/// frontier nodes (or destination set). This is the set of nodes which should

/// be propagated to the next step / builder. They are the nodes which have been

/// added to the builder (either as the input node set or as the newly

/// constructed nodes) but did not have any outgoing transitions added.

class NodeBuilder {

  virtual void anchor();

protected:

  const NodeBuilderContext &C;

  /// Specifies if the builder results have been finalized. For example, if it

  /// is set to false, autotransitions are yet to be generated.

  bool Finalized;

  bool HasGeneratedNodes = false;

  /// The frontier set - a set of nodes which need to be propagated after

  /// the builder dies.

  ExplodedNodeSet &Frontier;

  /// Checks if the results are ready.

  virtual bool checkResults() {

    return Finalized;

  }

  bool hasNoSinksInFrontier() {

    for (const auto  I : Frontier)

      if (I->isSink())

        return false;

    return true;

  }

  /// Allow subclasses to finalize results before result_begin() is executed.

  virtual void finalizeResults() {}

  ExplodedNode *generateNodeImpl(const ProgramPoint &PP,

                                 ProgramStateRef State,

                                 ExplodedNode *Pred,

                                 bool MarkAsSink = false);

public:

  NodeBuilder(ExplodedNode *SrcNode, ExplodedNodeSet &DstSet,

              const NodeBuilderContext &Ctx, bool F = true)

      : C(Ctx), Finalized(F), Frontier(DstSet) {

    Frontier.Add(SrcNode);

  }

  NodeBuilder(const ExplodedNodeSet &SrcSet, ExplodedNodeSet &DstSet,

              const NodeBuilderContext &Ctx, bool F = true)

      : C(Ctx), Finalized(F), Frontier(DstSet) {

    Frontier.insert(SrcSet);

    assert(hasNoSinksInFrontier());

  }

  virtual ~NodeBuilder() = default;

  /// Generates a node in the ExplodedGraph.

  ExplodedNode *generateNode(const ProgramPoint &PP,

                             ProgramStateRef State,

                             ExplodedNode *Pred) {

    return generateNodeImpl(

        PP, State, Pred,

        /*MarkAsSink=*/State->isPosteriorlyOverconstrained());

  }

  /// Generates a sink in the ExplodedGraph.

  ///

  /// When a node is marked as sink, the exploration from the node is stopped -

  /// the node becomes the last node on the path and certain kinds of bugs are

  /// suppressed.

  ExplodedNode *generateSink(const ProgramPoint &PP,

                             ProgramStateRef State,

                             ExplodedNode *Pred) {

    return generateNodeImpl(PP, State, Pred, true);

  }

  const ExplodedNodeSet &getResults() {

    finalizeResults();

    assert(checkResults());

    return Frontier;

  }

  using iterator = ExplodedNodeSet::iterator;

  /// Iterators through the results frontier.

  iterator begin() {

    finalizeResults();

    assert(checkResults());

    return Frontier.begin();

  }

  iterator end() {

    finalizeResults();

    return Frontier.end();

  }

  const NodeBuilderContext &getContext() { return C; }

  bool hasGeneratedNodes() { return HasGeneratedNodes; }

  void takeNodes(const ExplodedNodeSet &S) {

    for (const auto I : S)

      Frontier.erase(I);

  }

  void takeNodes(ExplodedNode *N) { Frontier.erase(N); }

  void addNodes(const ExplodedNodeSet &S) { Frontier.insert(S); }

  void addNodes(ExplodedNode *N) { Frontier.Add(N); }

};

/// \class NodeBuilderWithSinks

/// This node builder keeps track of the generated sink nodes.

class NodeBuilderWithSinks: public NodeBuilder {

  void anchor() override;

protected:

  SmallVector<ExplodedNode*, 2> sinksGenerated;

  ProgramPoint &Location;

public:

  NodeBuilderWithSinks(ExplodedNode *Pred, ExplodedNodeSet &DstSet,

                       const NodeBuilderContext &Ctx, ProgramPoint &L)

      : NodeBuilder(Pred, DstSet, Ctx), Location(L) {}

  ExplodedNode *generateNode(ProgramStateRef State,

                             ExplodedNode *Pred,

                             const ProgramPointTag *Tag = nullptr) {

    const ProgramPoint &LocalLoc = (Tag ? Location.withTag(Tag) : Location);

    return NodeBuilder::generateNode(LocalLoc, State, Pred);

  }

  ExplodedNode *generateSink(ProgramStateRef State, ExplodedNode *Pred,

                             const ProgramPointTag *Tag = nullptr) {

    const ProgramPoint &LocalLoc = (Tag ? Location.withTag(Tag) : Location);

    ExplodedNode *N = NodeBuilder::generateSink(LocalLoc, State, Pred);

    if (N && N->isSink())

      sinksGenerated.push_back(N);

    return N;

  }

  const SmallVectorImpl<ExplodedNode*> &getSinks() const {

    return sinksGenerated;

  }

};

/// \class StmtNodeBuilder

/// This builder class is useful for generating nodes that resulted from

/// visiting a statement. The main difference from its parent NodeBuilder is

/// that it creates a statement specific ProgramPoint.

class StmtNodeBuilder: public NodeBuilder {

  NodeBuilder *EnclosingBldr;

public:

  /// Constructs a StmtNodeBuilder. If the builder is going to process

  /// nodes currently owned by another builder(with larger scope), use

  /// Enclosing builder to transfer ownership.

  StmtNodeBuilder(ExplodedNode *SrcNode, ExplodedNodeSet &DstSet,

                  const NodeBuilderContext &Ctx,

                  NodeBuilder *Enclosing = nullptr)

      : NodeBuilder(SrcNode, DstSet, Ctx), EnclosingBldr(Enclosing) {

    if (EnclosingBldr)

      EnclosingBldr->takeNodes(SrcNode);

  }

  StmtNodeBuilder(ExplodedNodeSet &SrcSet, ExplodedNodeSet &DstSet,

                  const NodeBuilderContext &Ctx,

                  NodeBuilder *Enclosing = nullptr)

      : NodeBuilder(SrcSet, DstSet, Ctx), EnclosingBldr(Enclosing) {

    if (EnclosingBldr)

      for (const auto I : SrcSet)

        EnclosingBldr->takeNodes(I);

  }

  ~StmtNodeBuilder() override;

  using NodeBuilder::generateNode;

  using NodeBuilder::generateSink;

  ExplodedNode *generateNode(const Stmt *S,

                             ExplodedNode *Pred,

                             ProgramStateRef St,

                             const ProgramPointTag *tag = nullptr,

                             ProgramPoint::Kind K = ProgramPoint::PostStmtKind){

    const ProgramPoint &L = ProgramPoint::getProgramPoint(S, K,

                                  Pred->getLocationContext(), tag);

    return NodeBuilder::generateNode(L, St, Pred);

  }

  ExplodedNode *generateSink(const Stmt *S,

                             ExplodedNode *Pred,

                             ProgramStateRef St,

                             const ProgramPointTag *tag = nullptr,

                             ProgramPoint::Kind K = ProgramPoint::PostStmtKind){

    const ProgramPoint &L = ProgramPoint::getProgramPoint(S, K,

                                  Pred->getLocationContext(), tag);

    return NodeBuilder::generateSink(L, St, Pred);

  }

};

/// BranchNodeBuilder is responsible for constructing the nodes

/// corresponding to the two branches of the if statement - true and false.

class BranchNodeBuilder: public NodeBuilder {

  const CFGBlock *DstT;

  const CFGBlock *DstF;

  bool InFeasibleTrue;

  bool InFeasibleFalse;

  void anchor() override;

public:

  BranchNodeBuilder(ExplodedNode *SrcNode, ExplodedNodeSet &DstSet,

                    const NodeBuilderContext &C,

                    const CFGBlock *dstT, const CFGBlock *dstF)

      : NodeBuilder(SrcNode, DstSet, C), DstT(dstT), DstF(dstF),

        InFeasibleTrue(!DstT), InFeasibleFalse(!DstF) {

    // The branch node builder does not generate autotransitions.

    // If there are no successors it means that both branches are infeasible.

    takeNodes(SrcNode);

  }

  BranchNodeBuilder(const ExplodedNodeSet &SrcSet, ExplodedNodeSet &DstSet,

                    const NodeBuilderContext &C,

                    const CFGBlock *dstT, const CFGBlock *dstF)

      : NodeBuilder(SrcSet, DstSet, C), DstT(dstT), DstF(dstF),

        InFeasibleTrue(!DstT), InFeasibleFalse(!DstF) {

    takeNodes(SrcSet);

  }

  ExplodedNode *generateNode(ProgramStateRef State, bool branch,

                             ExplodedNode *Pred);

  const CFGBlock *getTargetBlock(bool branch) const {

    return branch ? DstT : DstF;

  }

  void markInfeasible(bool branch) {

    if (branch)

      InFeasibleTrue = true;

    else

      InFeasibleFalse = true;

  }

  bool isFeasible(bool branch) {

    return branch ? !InFeasibleTrue : !InFeasibleFalse;

  }

};

class IndirectGotoNodeBuilder {

  CoreEngine& Eng;

  const CFGBlock *Src;

  const CFGBlock &DispatchBlock;

  const Expr *E;

  ExplodedNode *Pred;

public:

  IndirectGotoNodeBuilder(ExplodedNode *pred, const CFGBlock *src,

                    const Expr *e, const CFGBlock *dispatch, CoreEngine* eng)

      : Eng(*eng), Src(src), DispatchBlock(*dispatch), E(e), Pred(pred) {}

  class iterator {

    friend class IndirectGotoNodeBuilder;

    CFGBlock::const_succ_iterator I;

    iterator(CFGBlock::const_succ_iterator i) : I(i) {}

  public:

    iterator &operator++() { ++I; return *this; }

    bool operator!=(const iterator &X) const { return I != X.I; }

    const LabelDecl *getLabel() const {

      return cast<LabelStmt>((*I)->getLabel())->getDecl();

    }

    const CFGBlock *getBlock() const {

      return *I;

    }

  };

  iterator begin() { return iterator(DispatchBlock.succ_begin()); }

  iterator end() { return iterator(DispatchBlock.succ_end()); }

  ExplodedNode *generateNode(const iterator &I,

                             ProgramStateRef State,

                             bool isSink = false);

  const Expr *getTarget() const { return E; }

  ProgramStateRef getState() const { return Pred->State; }

  const LocationContext *getLocationContext() const {

    return Pred->getLocationContext();

  }

};

class SwitchNodeBuilder {

  CoreEngine& Eng;

  const CFGBlock *Src;

  const Expr *Condition;

  ExplodedNode *Pred;

public:

  SwitchNodeBuilder(ExplodedNode *pred, const CFGBlock *src,

                    const Expr *condition, CoreEngine* eng)

      : Eng(*eng), Src(src), Condition(condition), Pred(pred) {}

  class iterator {

    friend class SwitchNodeBuilder;

    CFGBlock::const_succ_reverse_iterator I;

    iterator(CFGBlock::const_succ_reverse_iterator i) : I(i) {}

  public:

    iterator &operator++() { ++I; return *this; }

    bool operator!=(const iterator &X) const { return I != X.I; }

    bool operator==(const iterator &X) const { return I == X.I; }

    const CaseStmt *getCase() const {

      return cast<CaseStmt>((*I)->getLabel());

    }

    const CFGBlock *getBlock() const {

      return *I;

    }

  };

  iterator begin() { return iterator(Src->succ_rbegin()+1); }

  iterator end() { return iterator(Src->succ_rend()); }

  const SwitchStmt *getSwitch() const {

    return cast<SwitchStmt>(Src->getTerminator());

  }

  ExplodedNode *generateCaseStmtNode(const iterator &I,

                                     ProgramStateRef State);

  ExplodedNode *generateDefaultCaseNode(ProgramStateRef State,

                                        bool isSink = false);

  const Expr *getCondition() const { return Condition; }

  ProgramStateRef getState() const { return Pred->State; }

  const LocationContext *getLocationContext() const {

    return Pred->getLocationContext();

  }

};

} // namespace ento

} // namespace clang

#endif // LLVM_CLANG_STATICANALYZER_CORE_PATHSENSITIVE_COREENGINE_H