ExprEngineCallAndReturn.cpp

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//=-- ExprEngineCallAndReturn.cpp - Support for call/return -----*- 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 ExprEngine's support for calls and returns.
//
//===----------------------------------------------------------------------===//
 
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/Analysis/Analyses/LiveVariables.h"
#include "clang/Analysis/ConstructionContext.h"
#include "clang/StaticAnalyzer/Core/CheckerManager.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/DynamicExtent.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/EntryPointStats.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ExprEngine.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/SaveAndRestore.h"
#include <optional>
 
using namespace clang;
using namespace ento;
 
#define DEBUG_TYPE "ExprEngine"
 
STAT_COUNTER(
    NumOfDynamicDispatchPathSplits,
    "The # of times we split the path due to imprecise dynamic dispatch info");
 
STAT_COUNTER(NumInlinedCalls, "The # of times we inlined a call");
 
STAT_COUNTER(NumReachedInlineCountMax,
             "The # of times we reached inline count maximum");
 
void ExprEngine::processCallEnter(CallEnter CE, ExplodedNode *Pred) {
  // Get the entry block in the CFG of the callee.
  const CFGBlock *Entry = CE.getEntry();
 
  // Validate the CFG.
  assert(Entry->empty());
  assert(Entry->succ_size() == 1);
 
  // Get the solitary successor.
  const CFGBlock *Succ = *(Entry->succ_begin());
 
  // Construct an edge representing the starting location in the callee.
  BlockEdge Loc(Entry, Succ, CE.getCalleeStackFrame());
 
  ProgramStateRef state = Pred->getState();
 
  // Construct a new node, notify checkers that analysis of the function has
  // begun, and add the resultant nodes to the worklist.
  bool isNew;
  ExplodedNode *Node = G.getNode(Loc, state, false, &isNew);
  Node->addPredecessor(Pred, G);
  if (isNew) {
    // FIXME: In the `processBeginOfFunction` callback
    // `ExprEngine::getCurrStackFrame()` can be different from the
    // `StackFrame` queried from e.g. the `ExplodedNode`s. I'm not
    // touching this now because this commit is NFC; but in the future it would
    // be nice to avoid this inconsistency.
    ExplodedNodeSet DstBegin;
    processBeginOfFunction(Node, DstBegin, Loc);
    Engine.enqueue(DstBegin);
  }
}
 
// Find the last statement on the path to the exploded node and the
// corresponding Block.
static std::pair<const Stmt*,
                 const CFGBlock*> getLastStmt(const ExplodedNode *Node) {
  const Stmt *S = nullptr;
  const CFGBlock *Blk = nullptr;
  const StackFrame *SF = Node->getStackFrame();
 
  // Back up through the ExplodedGraph until we reach a statement node in this
  // stack frame.
  while (Node) {
    const ProgramPoint &PP = Node->getLocation();
 
    if (PP.getStackFrame() == SF) {
      if (std::optional<StmtPoint> SP = PP.getAs<StmtPoint>()) {
        S = SP->getStmt();
        break;
      } else if (std::optional<CallExitEnd> CEE = PP.getAs<CallExitEnd>()) {
        S = CEE->getCalleeStackFrame()->getCallSite();
        if (S)
          break;
 
        // If there is no statement, this is an implicitly-generated call.
        // We'll walk backwards over it and then continue the loop to find
        // an actual statement.
        std::optional<CallEnter> CE;
        do {
          Node = Node->getFirstPred();
          CE = Node->getLocationAs<CallEnter>();
        } while (!CE ||
                 CE->getCalleeStackFrame() != CEE->getCalleeStackFrame());
 
        // Continue searching the graph.
      } else if (std::optional<BlockEdge> BE = PP.getAs<BlockEdge>()) {
        Blk = BE->getSrc();
      }
    } else if (std::optional<CallEnter> CE = PP.getAs<CallEnter>()) {
      // If we reached the CallEnter for this function, it has no statements.
      if (CE->getCalleeStackFrame() == SF)
        break;
    }
 
    if (Node->pred_empty())
      return std::make_pair(nullptr, nullptr);
 
    Node = *Node->pred_begin();
  }
 
  return std::make_pair(S, Blk);
}
 
/// Adjusts a return value when the called function's return type does not
/// match the caller's expression type. This can happen when a dynamic call
/// is devirtualized, and the overriding method has a covariant (more specific)
/// return type than the parent's method. For C++ objects, this means we need
/// to add base casts.
static SVal adjustReturnValue(SVal V, QualType ExpectedTy, QualType ActualTy,
                              StoreManager &StoreMgr) {
  // For now, the only adjustments we handle apply only to locations.
  if (!isa<Loc>(V))
    return V;
 
  // If the types already match, don't do any unnecessary work.
  ExpectedTy = ExpectedTy.getCanonicalType();
  ActualTy = ActualTy.getCanonicalType();
  if (ExpectedTy == ActualTy)
    return V;
 
  // No adjustment is needed between Objective-C pointer types.
  if (ExpectedTy->isObjCObjectPointerType() &&
      ActualTy->isObjCObjectPointerType())
    return V;
 
  // C++ object pointers may need "derived-to-base" casts.
  const CXXRecordDecl *ExpectedClass = ExpectedTy->getPointeeCXXRecordDecl();
  const CXXRecordDecl *ActualClass = ActualTy->getPointeeCXXRecordDecl();
  if (ExpectedClass && ActualClass) {
    CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,
                       /*DetectVirtual=*/false);
    if (ActualClass->isDerivedFrom(ExpectedClass, Paths) &&
        !Paths.isAmbiguous(ActualTy->getCanonicalTypeUnqualified())) {
      return StoreMgr.evalDerivedToBase(V, Paths.front());
    }
  }
 
  // Unfortunately, Objective-C does not enforce that overridden methods have
  // covariant return types, so we can't assert that that never happens.
  // Be safe and return UnknownVal().
  return UnknownVal();
}
 
void ExprEngine::removeDeadOnEndOfFunction(ExplodedNode *Pred,
                                           ExplodedNodeSet &Dst) {
  // Find the last statement in the function and the corresponding basic block.
  const Stmt *LastSt = nullptr;
  const CFGBlock *Blk = nullptr;
  std::tie(LastSt, Blk) = getLastStmt(Pred);
  if (!Blk || !LastSt) {
    Dst.insert(Pred);
    return;
  }
 
  // Here, we destroy the current stack frame. We use the current function's
  // entire body as a diagnostic statement, with which the program point
  // will be associated. However, we only want to use LastStmt as a reference
  // for what to clean up if it's a ReturnStmt; otherwise, everything is dead.
  const StackFrame *SF = Pred->getStackFrame();
  removeDead(Pred, Dst, dyn_cast<ReturnStmt>(LastSt), SF,
             SF->getAnalysisDeclContext()->getBody(),
             ProgramPoint::PostStmtPurgeDeadSymbolsKind);
}
 
static bool wasDifferentDeclUsedForInlining(CallEventRef<> Call,
                                            const StackFrame *calleeCtx) {
  const Decl *RuntimeCallee = calleeCtx->getDecl();
  const Decl *StaticDecl = Call->getDecl();
  assert(RuntimeCallee);
  if (!StaticDecl)
    return true;
  return RuntimeCallee->getCanonicalDecl() != StaticDecl->getCanonicalDecl();
}
 
// Returns the number of elements in the array currently being destructed.
// If the element count is not found 0 will be returned.
static unsigned getElementCountOfArrayBeingDestructed(
    const CallEvent &Call, const ProgramStateRef State, SValBuilder &SVB) {
  assert(isa<CXXDestructorCall>(Call) &&
         "The call event is not a destructor call!");
 
  const auto &DtorCall = cast<CXXDestructorCall>(Call);
 
  auto ThisVal = DtorCall.getCXXThisVal();
 
  if (auto ThisElementRegion = dyn_cast<ElementRegion>(ThisVal.getAsRegion())) {
    auto ArrayRegion = ThisElementRegion->getAsArrayOffset().getRegion();
    auto ElementType = ThisElementRegion->getElementType();
 
    auto ElementCount =
        getDynamicElementCount(State, ArrayRegion, SVB, ElementType);
 
    if (!ElementCount.isConstant())
      return 0;
 
    return ElementCount.getAsInteger()->getLimitedValue();
  }
 
  return 0;
}
 
ProgramStateRef ExprEngine::removeStateTraitsUsedForArrayEvaluation(
    ProgramStateRef State, const CXXConstructExpr *E, const StackFrame *SF) {
 
  assert(SF && "Stack frame must be provided!");
 
  if (E) {
    if (getPendingInitLoop(State, E, SF))
      State = removePendingInitLoop(State, E, SF);
 
    if (getIndexOfElementToConstruct(State, E, SF))
      State = removeIndexOfElementToConstruct(State, E, SF);
  }
 
  if (getPendingArrayDestruction(State, SF))
    State = removePendingArrayDestruction(State, SF);
 
  return State;
}
 
/// The call exit is simulated with a sequence of nodes, which occur between
/// CallExitBegin and CallExitEnd. The following operations occur between the
/// two program points:
/// 1. CallExitBegin (triggers the start of call exit sequence)
/// 2. Bind the return value
/// 3. Run Remove dead bindings to clean up the dead symbols from the callee.
/// 4. CallExitEnd
/// 5. PostStmt<CallExpr>
/// Steps 1-3. happen in the callee stack frame; but there is a stack frame
/// switch and steps 4-5. happen in the caller stack frame.
void ExprEngine::processCallExit(ExplodedNode *CEBNode) {
  // Step 1 CEBNode was generated before the call.
  const StackFrame *CalleeSF = CEBNode->getStackFrame();
 
  const StackFrame *CallerSF = CalleeSF->getParent();
 
  const Expr *CE = CalleeSF->getCallSite();
  ProgramStateRef State = CEBNode->getState();
  // Find the last statement in the function and the corresponding basic block.
  auto [LastSt, Blk] = getLastStmt(CEBNode);
 
  const CFGBlock *PrePurgeBlock =
      isa_and_nonnull<ReturnStmt>(LastSt) ? Blk : &CEBNode->getCFG().getExit();
  // The first half of this process happens in the callee stack frame:
  setCurrStackFrameAndBlock(CalleeSF, PrePurgeBlock);
 
  // Generate a CallEvent /before/ cleaning the State, so that we can get the
  // correct value for 'this' (if necessary).
  CallEventManager &CEMgr = getStateManager().getCallEventManager();
  CallEventRef<> Call = CEMgr.getCaller(CalleeSF, State);
 
  // Step 2: generate node with bound return value: CEBNode -> BoundRetNode.
 
  // If this variable is set to 'true' the analyzer will evaluate the call
  // statement we are about to exit again, instead of continuing the execution
  // from the statement after the call. This is useful for non-POD type array
  // construction where the CXXConstructExpr is referenced only once in the CFG,
  // but we want to evaluate it as many times as many elements the array has.
  bool ShouldRepeatCall = false;
 
  if (const auto *DtorDecl =
          dyn_cast_or_null<CXXDestructorDecl>(Call->getDecl())) {
    if (auto Idx = getPendingArrayDestruction(State, CallerSF)) {
      ShouldRepeatCall = *Idx > 0;
 
      auto ThisVal = svalBuilder.getCXXThis(DtorDecl->getParent(), CalleeSF);
      State = State->killBinding(ThisVal);
    }
  }
 
  // If the callee returns an expression, bind its value to CallExpr.
  if (CE) {
    if (const ReturnStmt *RS = dyn_cast_or_null<ReturnStmt>(LastSt)) {
      const StackFrame *SF = CEBNode->getStackFrame();
 
      SVal V = UndefinedVal();
      if (RS->getRetValue())
        V = State->getSVal(RS->getRetValue(), SF);
 
      // Ensure that the return type matches the type of the returned Expr.
      if (wasDifferentDeclUsedForInlining(Call, CalleeSF)) {
        QualType ReturnedTy =
            CallEvent::getDeclaredResultType(CalleeSF->getDecl());
        if (!ReturnedTy.isNull()) {
          V = adjustReturnValue(V, CE->getType(), ReturnedTy,
                                getStoreManager());
        }
      }
 
      State = State->BindExpr(CE, CallerSF, V);
    }
 
    // Bind the constructed object value to CXXConstructExpr.
    if (const CXXConstructExpr *CCE = dyn_cast<CXXConstructExpr>(CE)) {
      loc::MemRegionVal This =
          svalBuilder.getCXXThis(CCE->getConstructor()->getParent(), CalleeSF);
      SVal ThisV = State->getSVal(This);
      ThisV = State->getSVal(ThisV.castAs<Loc>());
      State = State->BindExpr(CCE, CallerSF, ThisV);
 
      ShouldRepeatCall = shouldRepeatCtorCall(State, CCE, CallerSF);
    }
 
    if (const auto *CNE = dyn_cast<CXXNewExpr>(CE)) {
      // We are currently evaluating a CXXNewAllocator CFGElement. It takes a
      // while to reach the actual CXXNewExpr element from here, so keep the
      // region for later use.
      // Additionally cast the return value of the inlined operator new
      // (which is of type 'void *') to the correct object type.
      SVal AllocV = State->getSVal(CNE, CallerSF);
      AllocV = svalBuilder.evalCast(
          AllocV, CNE->getType(),
          getContext().getPointerType(getContext().VoidTy));
 
      State =
          addObjectUnderConstruction(State, CNE, CalleeSF->getParent(), AllocV);
    }
  }
 
  if (!ShouldRepeatCall) {
    State = removeStateTraitsUsedForArrayEvaluation(
        State, dyn_cast_or_null<CXXConstructExpr>(CE), CallerSF);
  }
 
  // Step 3: BoundRetNode -> CleanedNodes
  // If we can find a statement and a block in the inlined function, run remove
  // dead bindings before returning from the call. This is important to ensure
  // that we report the issues such as leaks in the stack frames in which
  // they occurred.
  ExplodedNodeSet CleanedNodes;
  if (LastSt && Blk && AMgr.options.AnalysisPurgeOpt != PurgeNone) {
    static SimpleProgramPointTag RetValBind("ExprEngine", "Bind Return Value");
    auto Loc = isa<ReturnStmt>(LastSt)
                   ? ProgramPoint{PostStmt(LastSt, CalleeSF, &RetValBind)}
                   : ProgramPoint{EpsilonPoint(CalleeSF, /*Data1=*/nullptr,
                                               /*Data2=*/nullptr, &RetValBind)};
 
    ExplodedNode *BoundRetNode = Engine.makeNode(Loc, State, CEBNode);
    if (!BoundRetNode)
      return;
 
    // We call removeDead in the stack frame of the callee.
    removeDead(BoundRetNode, CleanedNodes, /*ReferenceStmt=*/nullptr, CalleeSF,
               /*DiagnosticStmt=*/CalleeSF->getAnalysisDeclContext()->getBody(),
               ProgramPoint::PostStmtPurgeDeadSymbolsKind);
  } else {
    CleanedNodes.insert(CEBNode);
  }
 
  // The second half of this process happens in the caller stack frame. This is
  // an exception to the general rule that the current StackFrame and Block
  // stay the same within a single call to dispatchWorkItem.
  resetCurrStackFrameAndBlock();
  setCurrStackFrameAndBlock(CallerSF, CalleeSF->getCallSiteBlock());
  SaveAndRestore CBISave(currStmtIdx, CalleeSF->getIndex());
 
  for (ExplodedNode *N : CleanedNodes) {
    // Step 4: Generate the CallExitEnd node.
    // CleanedNodes -> CEENode
    CallExitEnd Loc(CalleeSF, CallerSF);
    ProgramStateRef CEEState = (N == CEBNode) ? State : N->getState();
 
    ExplodedNode *CEENode = Engine.makeNode(Loc, CEEState, N);
    if (!CEENode)
      continue;
 
    // Step 5: Perform the post-condition check of the CallExpr and enqueue the
    // result onto the work list.
    // CEENode -> Dst -> WorkList
 
    CallEventRef<> UpdatedCall = Call.cloneWithState(CEEState);
 
    ExplodedNodeSet DstPostPostCallCallback;
    getCheckerManager().runCheckersForPostCall(DstPostPostCallCallback, CEENode,
                                               *UpdatedCall, *this,
                                               /*wasInlined=*/true);
    ExplodedNodeSet DstPostCall;
    if (llvm::isa_and_nonnull<CXXNewExpr>(CE)) {
      for (ExplodedNode *I : DstPostPostCallCallback) {
        getCheckerManager().runCheckersForNewAllocator(
            cast<CXXAllocatorCall>(*UpdatedCall), DstPostCall, I, *this,
            /*wasInlined=*/true);
      }
    } else {
      DstPostCall.insert(DstPostPostCallCallback);
    }
 
    ExplodedNodeSet Dst;
    if (const ObjCMethodCall *Msg = dyn_cast<ObjCMethodCall>(Call)) {
      getCheckerManager().runCheckersForPostObjCMessage(Dst, DstPostCall, *Msg,
                                                        *this,
                                                        /*wasInlined=*/true);
    } else if (CE &&
               !(isa<CXXNewExpr>(CE) && // Called when visiting CXXNewExpr.
                 AMgr.getAnalyzerOptions().MayInlineCXXAllocator)) {
      getCheckerManager().runCheckersForPostStmt(Dst, DstPostCall, CE,
                                                 *this, /*wasInlined=*/true);
    } else {
      Dst.insert(DstPostCall);
    }
 
    // Enqueue the next element in the block.
    for (ExplodedNode *DstNode : Dst) {
      unsigned Idx = CalleeSF->getIndex() + (ShouldRepeatCall ? 0 : 1);
 
      Engine.getWorkList()->enqueue(DstNode, CalleeSF->getCallSiteBlock(), Idx);
    }
  }
}
 
bool ExprEngine::isSmall(AnalysisDeclContext *ADC) const {
  // When there are no branches in the function, it means that there's no
  // exponential complexity introduced by inlining such function.
  // Such functions also don't trigger various fundamental problems
  // with our inlining mechanism, such as the problem of
  // inlined defensive checks. Hence isLinear().
  const CFG *Cfg = ADC->getCFG();
  return Cfg->isLinear() || Cfg->size() <= AMgr.options.AlwaysInlineSize;
}
 
bool ExprEngine::isLarge(AnalysisDeclContext *ADC) const {
  const CFG *Cfg = ADC->getCFG();
  return Cfg->size() >= AMgr.options.MinCFGSizeTreatFunctionsAsLarge;
}
 
bool ExprEngine::isHuge(AnalysisDeclContext *ADC) const {
  const CFG *Cfg = ADC->getCFG();
  return Cfg->getNumBlockIDs() > AMgr.options.MaxInlinableSize;
}
 
void ExprEngine::examineStackFrames(
    const Decl *D, llvm::iterator_range<StackFrame::parent_iterator> Frames,
    bool &IsRecursive, unsigned &StackDepth) {
  IsRecursive = false;
  StackDepth = 0;
 
  for (const StackFrame &Frame : Frames) {
    const Decl *DI = Frame.getDecl();
 
    // Mark recursive (and mutually recursive) functions and always count
    // them when measuring the stack depth.
    if (DI == D) {
      IsRecursive = true;
      ++StackDepth;
      continue;
    }
 
    // Do not count the small functions when determining the stack depth.
    AnalysisDeclContext *CalleeADC = AMgr.getAnalysisDeclContext(DI);
    if (!isSmall(CalleeADC))
      ++StackDepth;
  }
}
 
// The GDM component containing the dynamic dispatch bifurcation info. When
// the exact type of the receiver is not known, we want to explore both paths -
// one on which we do inline it and the other one on which we don't. This is
// done to ensure we do not drop coverage.
// This is the map from the receiver region to a bool, specifying either we
// consider this region's information precise or not along the given path.
namespace {
  enum DynamicDispatchMode {
    DynamicDispatchModeInlined = 1,
    DynamicDispatchModeConservative
  };
} // end anonymous namespace
 
REGISTER_MAP_WITH_PROGRAMSTATE(DynamicDispatchBifurcationMap,
                               const MemRegion *, unsigned)
REGISTER_TRAIT_WITH_PROGRAMSTATE(CTUDispatchBifurcation, bool)
 
void ExprEngine::ctuBifurcate(const CallEvent &Call, const Decl *D,
                              ExplodedNodeSet &Dst, ExplodedNode *Pred,
                              ProgramStateRef State) {
  if (Call.isForeign() && !isSecondPhaseCTU()) {
    const auto IK = AMgr.options.getCTUPhase1Inlining();
    const bool DoInline = IK == CTUPhase1InliningKind::All ||
                          (IK == CTUPhase1InliningKind::Small &&
                           isSmall(AMgr.getAnalysisDeclContext(D)));
    if (DoInline) {
      inlineCall(Engine.getWorkList(), Call, D, Pred, State);
      return;
    }
    const bool BState = State->get<CTUDispatchBifurcation>();
    if (!BState) { // This is the first time we see this foreign function.
      // Enqueue it to be analyzed in the second (ctu) phase.
      inlineCall(Engine.getCTUWorkList(), Call, D, Pred, State);
      // Conservatively evaluate in the first phase.
      State = State->set<CTUDispatchBifurcation>(true);
    }
    Dst.insert(conservativeEvalCall(Call, Pred, State));
    return;
  }
  inlineCall(Engine.getWorkList(), Call, D, Pred, State);
}
 
void ExprEngine::inlineCall(WorkList *WList, const CallEvent &Call,
                            const Decl *D, ExplodedNode *Pred,
                            ProgramStateRef State) {
  assert(D);
 
  const StackFrame *CallerSF = Pred->getStackFrame();
  const BlockDataRegion *BlockInvocationData = nullptr;
  if (Call.getKind() == CE_Block &&
      !cast<BlockCall>(Call).isConversionFromLambda()) {
    BlockInvocationData = cast<BlockCall>(Call).getBlockRegion();
    assert(BlockInvocationData &&
           "If we have the block definition we should have its region");
  }
 
  // This may be NULL, but that's fine.
  const Expr *CallE = Call.getOriginExpr();
 
  // Construct a new stack frame for the callee.
  AnalysisDeclContext *CalleeADC = AMgr.getAnalysisDeclContext(D);
  const StackFrame *CalleeSF = CalleeADC->getStackFrame(
      CallerSF, BlockInvocationData, CallE, getCurrBlock(),
      getNumVisitedCurrent(), currStmtIdx);
 
  CallEnter Loc(CallE, CalleeSF, CallerSF);
 
  // Construct a new state which contains the mapping from actual to
  // formal arguments.
  State = State->enterStackFrame(Call, CalleeSF);
 
  bool isNew;
  if (ExplodedNode *N = G.getNode(Loc, State, false, &isNew)) {
    N->addPredecessor(Pred, G);
    if (isNew)
      WList->enqueue(N);
  }
 
  NumInlinedCalls++;
  Engine.FunctionSummaries->bumpNumTimesInlined(D);
 
  // Do not mark as visited in the 2nd run (CTUWList), so the function will
  // be visited as top-level, this way we won't loose reports in non-ctu
  // mode. Considering the case when a function in a foreign TU calls back
  // into the main TU.
  // Note, during the 1st run, it doesn't matter if we mark the foreign
  // functions as visited (or not) because they can never appear as a top level
  // function in the main TU.
  if (!isSecondPhaseCTU())
    // Mark the decl as visited.
    if (VisitedCallees)
      VisitedCallees->insert(D);
}
 
static ProgramStateRef getInlineFailedState(ProgramStateRef State,
                                            const Expr *CallE) {
  const void *ReplayState = State->get<ReplayWithoutInlining>();
  if (!ReplayState)
    return nullptr;
 
  assert(ReplayState == CallE && "Backtracked to the wrong call.");
  (void)CallE;
 
  return State->remove<ReplayWithoutInlining>();
}
 
void ExprEngine::VisitCallExpr(const CallExpr *CE, ExplodedNode *Pred,
                               ExplodedNodeSet &dst) {
  if (const auto *OCE = dyn_cast<CXXOperatorCallExpr>(CE)) {
    // For instance method operators, make sure the 'this' argument has a
    // valid region.
    // FIXME: Why is this only applied for operator calls and not other calls?
    const Decl *Callee = OCE->getCalleeDecl();
    if (const auto *MD = dyn_cast_or_null<CXXMethodDecl>(Callee)) {
      if (MD->isImplicitObjectMemberFunction()) {
        ProgramStateRef State = Pred->getState();
        const StackFrame *SF = Pred->getStackFrame();
        ProgramStateRef NewState =
            createTemporaryRegionIfNeeded(State, SF, OCE->getArg(0));
        if (NewState != State) {
          PreStmt PS(OCE, SF, /*tag=*/nullptr);
          Pred = Engine.makeNode(PS, NewState, Pred);
          if (!Pred)
            return; // Cached out.
        }
      }
    }
  }
  // Perform the previsit of the CallExpr.
  ExplodedNodeSet dstPreVisit;
  getCheckerManager().runCheckersForPreStmt(dstPreVisit, Pred, CE, *this);
 
  // Get the call in its initial state. We use this as a template to perform
  // all the checks.
  CallEventManager &CEMgr = getStateManager().getCallEventManager();
  CallEventRef<> CallTemplate = CEMgr.getSimpleCall(
      CE, Pred->getState(), Pred->getStackFrame(), getCFGElementRef());
 
  // Evaluate the function call.  We try each of the checkers
  // to see if the can evaluate the function call.
  ExplodedNodeSet dstCallEvaluated;
  for (ExplodedNode *N : dstPreVisit) {
    evalCall(dstCallEvaluated, N, *CallTemplate);
  }
 
  // Finally, perform the post-condition check of the CallExpr and store
  // the created nodes in 'Dst'.
  // Note that if the call was inlined, dstCallEvaluated will be empty.
  // The post-CallExpr check will occur in processCallExit.
  getCheckerManager().runCheckersForPostStmt(dst, dstCallEvaluated, CE,
                                             *this);
}
 
ProgramStateRef ExprEngine::finishArgumentConstruction(ProgramStateRef State,
                                                       const CallEvent &Call) {
  // WARNING: The state attached to 'Call' may be obsolete, do not call any
  // methods that rely on it!
  const Expr *E = Call.getOriginExpr();
  // FIXME: Constructors to placement arguments of operator new
  // are not supported yet.
  if (!E || isa<CXXNewExpr>(E))
    return State;
 
  const StackFrame *SF = Call.getStackFrame();
  for (unsigned CallI = 0, CallN = Call.getNumArgs(); CallI != CallN; ++CallI) {
    unsigned I = Call.getASTArgumentIndex(CallI);
    if (std::optional<SVal> V = getObjectUnderConstruction(State, {E, I}, SF)) {
      SVal VV = *V;
      (void)VV;
      assert(cast<VarRegion>(VV.castAs<loc::MemRegionVal>().getRegion())
                 ->getStackFrame()
                 ->getParent() == SF);
      State = finishObjectConstruction(State, {E, I}, SF);
    }
  }
 
  return State;
}
 
void ExprEngine::finishArgumentConstruction(ExplodedNodeSet &Dst,
                                            ExplodedNode *Pred,
                                            const CallEvent &Call) {
  // WARNING: The state attached to 'Call' may be obsolete, do not call any
  // methods that rely on it!
  ProgramStateRef State = Pred->getState();
  ProgramStateRef CleanedState = finishArgumentConstruction(State, Call);
  if (CleanedState == State) {
    Dst.insert(Pred);
    return;
  }
 
  const Expr *E = Call.getOriginExpr();
  const StackFrame *SF = Call.getStackFrame();
  static SimpleProgramPointTag Tag("ExprEngine",
                                   "Finish argument construction");
  Dst.insert(Engine.makeNode(PreStmt(E, SF, &Tag), CleanedState, Pred));
}
 
void ExprEngine::evalCall(ExplodedNodeSet &Dst, ExplodedNode *Pred,
                          const CallEvent &CallTemplate) {
  // NOTE: CallTemplate is called a "template" because its attached state may
  // be obsolete (compared to the state of Pred). The state-dependent methods
  // of CallEvent should be used only after a `cloneWithState` call that
  // attaches the up-to-date state to this template object.
 
  // Run any pre-call checks using the generic call interface.
  ExplodedNodeSet dstPreVisit;
  getCheckerManager().runCheckersForPreCall(dstPreVisit, Pred, CallTemplate,
                                            *this);
 
  // Actually evaluate the function call.  We try each of the checkers
  // to see if the can evaluate the function call, and get a callback at
  // defaultEvalCall if all of them fail.
  ExplodedNodeSet dstCallEvaluated;
  getCheckerManager().runCheckersForEvalCall(
      dstCallEvaluated, dstPreVisit, CallTemplate, *this, EvalCallOptions());
 
  // If there were other constructors called for object-type arguments
  // of this call, clean them up.
  ExplodedNodeSet dstArgumentCleanup;
  for (ExplodedNode *I : dstCallEvaluated)
    finishArgumentConstruction(dstArgumentCleanup, I, CallTemplate);
 
  ExplodedNodeSet dstPostCall;
  getCheckerManager().runCheckersForPostCall(dstPostCall, dstArgumentCleanup,
                                             CallTemplate, *this);
 
  // Escaping symbols conjured during invalidating the regions above.
  // Note that, for inlined calls the nodes were put back into the worklist,
  // so we can assume that every node belongs to a conservative call at this
  // point.
 
  // Run pointerEscape callback with the newly conjured symbols.
  SmallVector<std::pair<SVal, SVal>, 8> Escaped;
  for (ExplodedNode *I : dstPostCall) {
    ProgramStateRef State = I->getState();
    CallEventRef<> Call = CallTemplate.cloneWithState(State);
    Escaped.clear();
    {
      unsigned Arg = -1;
      for (const ParmVarDecl *PVD : Call->parameters()) {
        ++Arg;
        QualType ParamTy = PVD->getType();
        if (ParamTy.isNull() ||
            (!ParamTy->isPointerType() && !ParamTy->isReferenceType()))
          continue;
        QualType Pointee = ParamTy->getPointeeType();
        if (Pointee.isConstQualified() || Pointee->isVoidType())
          continue;
        if (const MemRegion *MR = Call->getArgSVal(Arg).getAsRegion())
          Escaped.emplace_back(loc::MemRegionVal(MR), State->getSVal(MR, Pointee));
      }
    }
 
    State = processPointerEscapedOnBind(State, Escaped, I->getStackFrame(),
                                        PSK_EscapeOutParameters, &*Call);
 
    if (State != I->getState())
      I = Engine.makeNode(I->getLocation(), State, I);
 
    Dst.insert(I);
  }
}
 
ProgramStateRef ExprEngine::bindReturnValue(const CallEvent &Call,
                                            const StackFrame *SF,
                                            ProgramStateRef State) {
  const Expr *E = Call.getOriginExpr();
  const ConstCFGElementRef &Elem = Call.getCFGElementRef();
  if (!E)
    return State;
 
  // Some method families have known return values.
  if (const ObjCMethodCall *Msg = dyn_cast<ObjCMethodCall>(&Call)) {
    switch (Msg->getMethodFamily()) {
    default:
      break;
    case OMF_autorelease:
    case OMF_retain:
    case OMF_self: {
      // These methods return their receivers.
      return State->BindExpr(E, SF, Msg->getReceiverSVal());
    }
    }
  } else if (const CXXConstructorCall *C = dyn_cast<CXXConstructorCall>(&Call)){
    SVal ThisV = C->getCXXThisVal();
    ThisV = State->getSVal(ThisV.castAs<Loc>());
    return State->BindExpr(E, SF, ThisV);
  }
 
  SVal R;
  QualType ResultTy = Call.getResultType();
  unsigned Count = getNumVisitedCurrent();
  if (auto RTC = getCurrentCFGElement().getAs<CFGCXXRecordTypedCall>()) {
    // Conjure a temporary if the function returns an object by value.
    SVal Target;
    assert(RTC->getStmt() == Call.getOriginExpr());
    EvalCallOptions CallOpts; // FIXME: We won't really need those.
    std::tie(State, Target) =
        handleConstructionContext(Call.getOriginExpr(), State, currBldrCtx, SF,
                                  RTC->getConstructionContext(), CallOpts);
    const MemRegion *TargetR = Target.getAsRegion();
    assert(TargetR);
    // Invalidate the region so that it didn't look uninitialized. If this is
    // a field or element constructor, we do not want to invalidate
    // the whole structure. Pointer escape is meaningless because
    // the structure is a product of conservative evaluation
    // and therefore contains nothing interesting at this point.
    RegionAndSymbolInvalidationTraits ITraits;
    ITraits.setTrait(TargetR,
        RegionAndSymbolInvalidationTraits::TK_DoNotInvalidateSuperRegion);
    State = State->invalidateRegions(TargetR, Elem, Count, SF,
                                     /* CausesPointerEscape=*/false, nullptr,
                                     &Call, &ITraits);
 
    R = State->getSVal(Target.castAs<Loc>(), E->getType());
  } else {
    // Conjure a symbol if the return value is unknown.
 
    // See if we need to conjure a heap pointer instead of
    // a regular unknown pointer.
    const auto *CNE = dyn_cast<CXXNewExpr>(E);
    if (CNE && CNE->getOperatorNew()->isReplaceableGlobalAllocationFunction()) {
      R = svalBuilder.getConjuredHeapSymbolVal(Elem, SF, E->getType(), Count);
      const MemRegion *MR = R.getAsRegion()->StripCasts();
 
      // Store the extent of the allocated object(s).
      SVal ElementCount;
      if (const Expr *SizeExpr = CNE->getArraySize().value_or(nullptr)) {
        ElementCount = State->getSVal(SizeExpr, SF);
      } else {
        ElementCount = svalBuilder.makeIntVal(1, /*IsUnsigned=*/true);
      }
 
      SVal ElementSize = getElementExtent(CNE->getAllocatedType(), svalBuilder);
 
      SVal Size =
          svalBuilder.evalBinOp(State, BO_Mul, ElementCount, ElementSize,
                                svalBuilder.getArrayIndexType());
 
      // FIXME: This line is to prevent a crash. For more details please check
      // issue #56264.
      if (Size.isUndef())
        Size = UnknownVal();
 
      State = setDynamicExtent(State, MR, Size.castAs<DefinedOrUnknownSVal>());
    } else {
      R = svalBuilder.conjureSymbolVal(Elem, SF, ResultTy, Count);
    }
  }
  return State->BindExpr(E, SF, R);
}
 
// Conservatively evaluate call by invalidating regions and binding
// a conjured return value.
ExplodedNode *ExprEngine::conservativeEvalCall(const CallEvent &Call,
                                               ExplodedNode *Pred,
                                               ProgramStateRef State) {
  State = Call.invalidateRegions(getNumVisitedCurrent(), State);
  State = bindReturnValue(Call, Pred->getStackFrame(), State);
 
  // And make the result node.
  static SimpleProgramPointTag PT("ExprEngine", "Conservative eval call");
  return Engine.makeNode(Call.getProgramPoint(false, &PT), State, Pred);
}
 
ExprEngine::CallInlinePolicy
ExprEngine::mayInlineCallKind(const CallEvent &Call, const ExplodedNode *Pred,
                              AnalyzerOptions &Opts,
                              const EvalCallOptions &CallOpts) {
  const StackFrame *CallerSF = Pred->getStackFrame();
  switch (Call.getKind()) {
  case CE_Function:
  case CE_CXXStaticOperator:
  case CE_Block:
    break;
  case CE_CXXMember:
  case CE_CXXMemberOperator:
    if (!Opts.mayInlineCXXMemberFunction(CIMK_MemberFunctions))
      return CIP_DisallowedAlways;
    break;
  case CE_CXXConstructor: {
    if (!Opts.mayInlineCXXMemberFunction(CIMK_Constructors))
      return CIP_DisallowedAlways;
 
    const CXXConstructorCall &Ctor = cast<CXXConstructorCall>(Call);
 
    const CXXConstructExpr *CtorExpr = Ctor.getOriginExpr();
 
    auto CCE = getCurrentCFGElement().getAs<CFGConstructor>();
    const ConstructionContext *CC = CCE ? CCE->getConstructionContext()
                                        : nullptr;
 
    if (llvm::isa_and_nonnull<NewAllocatedObjectConstructionContext>(CC) &&
        !Opts.MayInlineCXXAllocator)
      return CIP_DisallowedOnce;
 
    if (CallOpts.IsArrayCtorOrDtor) {
      if (!shouldInlineArrayConstruction(Pred->getState(), CtorExpr, CallerSF))
        return CIP_DisallowedOnce;
    }
 
    // Inlining constructors requires including initializers in the CFG.
    const AnalysisDeclContext *ADC = CallerSF->getAnalysisDeclContext();
    assert(ADC->getCFGBuildOptions().AddInitializers && "No CFG initializers");
    (void)ADC;
 
    // If the destructor is trivial, it's always safe to inline the constructor.
    if (Ctor.getDecl()->getParent()->hasTrivialDestructor())
      break;
 
    // For other types, only inline constructors if destructor inlining is
    // also enabled.
    if (!Opts.mayInlineCXXMemberFunction(CIMK_Destructors))
      return CIP_DisallowedAlways;
 
    if (CtorExpr->getConstructionKind() == CXXConstructionKind::Complete) {
      // If we don't handle temporary destructors, we shouldn't inline
      // their constructors.
      if (CallOpts.IsTemporaryCtorOrDtor &&
          !Opts.ShouldIncludeTemporaryDtorsInCFG)
        return CIP_DisallowedOnce;
 
      // If we did not find the correct this-region, it would be pointless
      // to inline the constructor. Instead we will simply invalidate
      // the fake temporary target.
      if (CallOpts.IsCtorOrDtorWithImproperlyModeledTargetRegion)
        return CIP_DisallowedOnce;
 
      // If the temporary is lifetime-extended by binding it to a reference-type
      // field within an aggregate, automatic destructors don't work properly.
      if (CallOpts.IsTemporaryLifetimeExtendedViaAggregate)
        return CIP_DisallowedOnce;
    }
 
    break;
  }
  case CE_CXXInheritedConstructor: {
    // This doesn't really increase the cost of inlining ever, because
    // the stack frame of the inherited constructor is trivial.
    return CIP_Allowed;
  }
  case CE_CXXDestructor: {
    if (!Opts.mayInlineCXXMemberFunction(CIMK_Destructors))
      return CIP_DisallowedAlways;
 
    // Inlining destructors requires building the CFG correctly.
    const AnalysisDeclContext *ADC = CallerSF->getAnalysisDeclContext();
    assert(ADC->getCFGBuildOptions().AddImplicitDtors && "No CFG destructors");
    (void)ADC;
 
    if (CallOpts.IsArrayCtorOrDtor) {
      if (!shouldInlineArrayDestruction(getElementCountOfArrayBeingDestructed(
              Call, Pred->getState(), svalBuilder))) {
        return CIP_DisallowedOnce;
      }
    }
 
    // Allow disabling temporary destructor inlining with a separate option.
    if (CallOpts.IsTemporaryCtorOrDtor &&
        !Opts.MayInlineCXXTemporaryDtors)
      return CIP_DisallowedOnce;
 
    // If we did not find the correct this-region, it would be pointless
    // to inline the destructor. Instead we will simply invalidate
    // the fake temporary target.
    if (CallOpts.IsCtorOrDtorWithImproperlyModeledTargetRegion)
      return CIP_DisallowedOnce;
    break;
  }
  case CE_CXXDeallocator:
    [[fallthrough]];
  case CE_CXXAllocator:
    if (Opts.MayInlineCXXAllocator)
      break;
    // Do not inline allocators until we model deallocators.
    // This is unfortunate, but basically necessary for smart pointers and such.
    return CIP_DisallowedAlways;
  case CE_ObjCMessage:
    if (!Opts.MayInlineObjCMethod)
      return CIP_DisallowedAlways;
    if (!(Opts.getIPAMode() == IPAK_DynamicDispatch ||
          Opts.getIPAMode() == IPAK_DynamicDispatchBifurcate))
      return CIP_DisallowedAlways;
    break;
  }
 
  return CIP_Allowed;
}
 
/// Returns true if the given C++ class contains a member with the given name.
static bool hasMember(const ASTContext &Ctx, const CXXRecordDecl *RD,
                      StringRef Name) {
  const IdentifierInfo &II = Ctx.Idents.get(Name);
  return RD->hasMemberName(Ctx.DeclarationNames.getIdentifier(&II));
}
 
/// Returns true if the given C++ class is a container or iterator.
///
/// Our heuristic for this is whether it contains a method named 'begin()' or a
/// nested type named 'iterator' or 'iterator_category'.
static bool isContainerClass(const ASTContext &Ctx, const CXXRecordDecl *RD) {
  return hasMember(Ctx, RD, "begin") ||
         hasMember(Ctx, RD, "iterator") ||
         hasMember(Ctx, RD, "iterator_category");
}
 
/// Returns true if the given function refers to a method of a C++ container
/// or iterator.
///
/// We generally do a poor job modeling most containers right now, and might
/// prefer not to inline their methods.
static bool isContainerMethod(const ASTContext &Ctx,
                              const FunctionDecl *FD) {
  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD))
    return isContainerClass(Ctx, MD->getParent());
  return false;
}
 
/// Returns true if the given function is the destructor of a class named
/// "shared_ptr".
static bool isCXXSharedPtrDtor(const FunctionDecl *FD) {
  const CXXDestructorDecl *Dtor = dyn_cast<CXXDestructorDecl>(FD);
  if (!Dtor)
    return false;
 
  const CXXRecordDecl *RD = Dtor->getParent();
  if (const IdentifierInfo *II = RD->getDeclName().getAsIdentifierInfo())
    if (II->isStr("shared_ptr"))
        return true;
 
  return false;
}
 
/// Returns true if the function in \p CalleeADC may be inlined in general.
///
/// This checks static properties of the function, such as its signature and
/// CFG, to determine whether the analyzer should ever consider inlining it,
/// in any context.
bool ExprEngine::mayInlineDecl(AnalysisDeclContext *CalleeADC) const {
  AnalyzerOptions &Opts = AMgr.getAnalyzerOptions();
  // FIXME: Do not inline variadic calls.
  if (CallEvent::isVariadic(CalleeADC->getDecl()))
    return false;
 
  // Check certain C++-related inlining policies.
  ASTContext &Ctx = CalleeADC->getASTContext();
  if (Ctx.getLangOpts().CPlusPlus) {
    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(CalleeADC->getDecl())) {
      // Conditionally control the inlining of template functions.
      if (!Opts.MayInlineTemplateFunctions)
        if (FD->getTemplatedKind() != FunctionDecl::TK_NonTemplate)
          return false;
 
      // Conditionally control the inlining of C++ standard library functions.
      if (!Opts.MayInlineCXXStandardLibrary)
        if (Ctx.getSourceManager().isInSystemHeader(FD->getLocation()))
          if (AnalysisDeclContext::isInStdNamespace(FD))
            return false;
 
      // Conditionally control the inlining of methods on objects that look
      // like C++ containers.
      if (!Opts.MayInlineCXXContainerMethods)
        if (!AMgr.isInCodeFile(FD->getLocation()))
          if (isContainerMethod(Ctx, FD))
            return false;
 
      // Conditionally control the inlining of the destructor of C++ shared_ptr.
      // We don't currently do a good job modeling shared_ptr because we can't
      // see the reference count, so treating as opaque is probably the best
      // idea.
      if (!Opts.MayInlineCXXSharedPtrDtor)
        if (isCXXSharedPtrDtor(FD))
          return false;
    }
  }
 
  // It is possible that the CFG cannot be constructed.
  // Be safe, and check if the CalleeCFG is valid.
  const CFG *CalleeCFG = CalleeADC->getCFG();
  if (!CalleeCFG)
    return false;
 
  // Do not inline large functions.
  if (isHuge(CalleeADC))
    return false;
 
  // It is possible that the live variables analysis cannot be
  // run.  If so, bail out.
  if (!CalleeADC->getAnalysis<RelaxedLiveVariables>())
    return false;
 
  return true;
}
 
bool ExprEngine::shouldInlineCall(const CallEvent &Call, const Decl *D,
                                  const ExplodedNode *Pred,
                                  const EvalCallOptions &CallOpts) {
  if (!D)
    return false;
 
  AnalysisManager &AMgr = getAnalysisManager();
  AnalyzerOptions &Opts = AMgr.options;
  AnalysisDeclContextManager &ADCMgr = AMgr.getAnalysisDeclContextManager();
  AnalysisDeclContext *CalleeADC = ADCMgr.getContext(D);
 
  // The auto-synthesized bodies are essential to inline as they are
  // usually small and commonly used. Note: we should do this check early on to
  // ensure we always inline these calls.
  if (CalleeADC->isBodyAutosynthesized())
    return true;
 
  if (!AMgr.shouldInlineCall())
    return false;
 
  // Check if this function has been marked as non-inlinable.
  std::optional<bool> MayInline = Engine.FunctionSummaries->mayInline(D);
  if (MayInline) {
    if (!*MayInline)
      return false;
 
  } else {
    // We haven't actually checked the static properties of this function yet.
    // Do that now, and record our decision in the function summaries.
    if (mayInlineDecl(CalleeADC)) {
      Engine.FunctionSummaries->markMayInline(D);
    } else {
      Engine.FunctionSummaries->markShouldNotInline(D);
      return false;
    }
  }
 
  // Check if we should inline a call based on its kind.
  // FIXME: this checks both static and dynamic properties of the call, which
  // means we're redoing a bit of work that could be cached in the function
  // summary.
  CallInlinePolicy CIP = mayInlineCallKind(Call, Pred, Opts, CallOpts);
  if (CIP != CIP_Allowed) {
    if (CIP == CIP_DisallowedAlways) {
      assert(!MayInline || *MayInline);
      Engine.FunctionSummaries->markShouldNotInline(D);
    }
    return false;
  }
 
  // Do not inline if recursive or we've reached max stack frame count.
  bool IsRecursive = false;
  unsigned StackDepth = 0;
  examineStackFrames(D, Pred->stackframes(), IsRecursive, StackDepth);
  if ((StackDepth >= Opts.InlineMaxStackDepth) &&
      (!isSmall(CalleeADC) || IsRecursive))
    return false;
 
  // Do not inline large functions too many times.
  if ((Engine.FunctionSummaries->getNumTimesInlined(D) >
       Opts.MaxTimesInlineLarge) &&
      isLarge(CalleeADC)) {
    NumReachedInlineCountMax++;
    return false;
  }
 
  if (HowToInline == Inline_Minimal && (!isSmall(CalleeADC) || IsRecursive))
    return false;
 
  return true;
}
 
bool ExprEngine::shouldInlineArrayConstruction(const ProgramStateRef State,
                                               const CXXConstructExpr *CE,
                                               const StackFrame *SF) {
  if (!CE)
    return false;
 
  // FIXME: Handle other arrays types.
  if (const auto *CAT = dyn_cast<ConstantArrayType>(CE->getType())) {
    unsigned ArrSize = getContext().getConstantArrayElementCount(CAT);
 
    // This might seem conter-intuitive at first glance, but the functions are
    // closely related. Reasoning about destructors depends only on the type
    // of the expression that initialized the memory region, which is the
    // CXXConstructExpr. So to avoid code repetition, the work is delegated
    // to the function that reasons about destructor inlining. Also note that
    // if the constructors of the array elements are inlined, the destructors
    // can also be inlined and if the destructors can be inline, it's safe to
    // inline the constructors.
    return shouldInlineArrayDestruction(ArrSize);
  }
 
  // Check if we're inside an ArrayInitLoopExpr, and it's sufficiently small.
  if (auto Size = getPendingInitLoop(State, CE, SF))
    return shouldInlineArrayDestruction(*Size);
 
  return false;
}
 
bool ExprEngine::shouldInlineArrayDestruction(uint64_t Size) {
 
  uint64_t maxAllowedSize = AMgr.options.maxBlockVisitOnPath;
 
  // Declaring a 0 element array is also possible.
  return Size <= maxAllowedSize && Size > 0;
}
 
bool ExprEngine::shouldRepeatCtorCall(ProgramStateRef State,
                                      const CXXConstructExpr *E,
                                      const StackFrame *SF) {
 
  if (!E)
    return false;
 
  auto Ty = E->getType();
 
  // FIXME: Handle non constant array types
  if (const auto *CAT = dyn_cast<ConstantArrayType>(Ty)) {
    unsigned Size = getContext().getConstantArrayElementCount(CAT);
    return Size > getIndexOfElementToConstruct(State, E, SF);
  }
 
  if (auto Size = getPendingInitLoop(State, E, SF))
    return Size > getIndexOfElementToConstruct(State, E, SF);
 
  return false;
}
 
static bool isTrivialObjectAssignment(const CallEvent &Call) {
  const CXXInstanceCall *ICall = dyn_cast<CXXInstanceCall>(&Call);
  if (!ICall)
    return false;
 
  const CXXMethodDecl *MD = dyn_cast_or_null<CXXMethodDecl>(ICall->getDecl());
  if (!MD)
    return false;
  if (!(MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator()))
    return false;
 
  return MD->isTrivial();
}
 
void ExprEngine::defaultEvalCall(ExplodedNodeSet &Dst, ExplodedNode *Pred,
                                 const CallEvent &Call,
                                 const EvalCallOptions &CallOpts) {
  // Make sure we have the most recent state attached to the call.
  ProgramStateRef State = Pred->getState();
 
  // Special-case trivial assignment operators.
  if (isTrivialObjectAssignment(Call)) {
    performTrivialCopy(Dst, Pred, Call);
    return;
  }
 
  const Expr *E = Call.getOriginExpr();
 
  ProgramStateRef InlinedFailedState = getInlineFailedState(State, E);
  if (InlinedFailedState) {
    // If we already tried once and failed, make sure we don't retry later.
    State = InlinedFailedState;
  } else {
    RuntimeDefinition RD = Call.getRuntimeDefinition();
    Call.setForeign(RD.isForeign());
    const Decl *D = RD.getDecl();
    if (shouldInlineCall(Call, D, Pred, CallOpts)) {
      if (RD.mayHaveOtherDefinitions()) {
        AnalyzerOptions &Options = getAnalysisManager().options;
 
        // Explore with and without inlining the call.
        if (Options.getIPAMode() == IPAK_DynamicDispatchBifurcate) {
          dynDispatchBifurcate(RD.getDispatchRegion(), Call, D, Dst, Pred);
          return;
        }
 
        // Don't inline if we're not in any dynamic dispatch mode.
        if (Options.getIPAMode() != IPAK_DynamicDispatch) {
          Dst.insert(conservativeEvalCall(Call, Pred, State));
          return;
        }
      }
      ctuBifurcate(Call, D, Dst, Pred, State);
      return;
    }
  }
 
  // If we can't inline it, clean up the state traits used only if the function
  // is inlined.
  State = removeStateTraitsUsedForArrayEvaluation(
      State, dyn_cast_or_null<CXXConstructExpr>(E), Call.getStackFrame());
 
  // Also handle the return value and invalidate the regions.
  Dst.insert(conservativeEvalCall(Call, Pred, State));
}
 
void ExprEngine::dynDispatchBifurcate(const MemRegion *BifurReg,
                                      const CallEvent &Call, const Decl *D,
                                      ExplodedNodeSet &Dst,
                                      ExplodedNode *Pred) {
  assert(BifurReg);
  BifurReg = BifurReg->StripCasts();
 
  // Check if we've performed the split already - note, we only want
  // to split the path once per memory region.
  ProgramStateRef State = Pred->getState();
  const unsigned *BState =
                        State->get<DynamicDispatchBifurcationMap>(BifurReg);
  if (BState) {
    // If we are on "inline path", keep inlining if possible.
    if (*BState == DynamicDispatchModeInlined)
      ctuBifurcate(Call, D, Dst, Pred, State);
    // If inline failed, or we are on the path where we assume we
    // don't have enough info about the receiver to inline, conjure the
    // return value and invalidate the regions.
    Dst.insert(conservativeEvalCall(Call, Pred, State));
    return;
  }
 
  // If we got here, this is the first time we process a message to this
  // region, so split the path.
  ProgramStateRef IState =
      State->set<DynamicDispatchBifurcationMap>(BifurReg,
                                               DynamicDispatchModeInlined);
  ctuBifurcate(Call, D, Dst, Pred, IState);
 
  ProgramStateRef NoIState =
      State->set<DynamicDispatchBifurcationMap>(BifurReg,
                                               DynamicDispatchModeConservative);
  Dst.insert(conservativeEvalCall(Call, Pred, NoIState));
 
  NumOfDynamicDispatchPathSplits++;
}
 
void ExprEngine::VisitReturnStmt(const ReturnStmt *RS, ExplodedNode *Pred,
                                 ExplodedNodeSet &Dst) {
  ExplodedNodeSet DstPreVisit;
  getCheckerManager().runCheckersForPreStmt(DstPreVisit, Pred, RS, *this);
 
  if (RS->getRetValue()) {
    for (ExplodedNode *N : DstPreVisit) {
      Dst.insert(Engine.makePostStmtNode(RS, N->getState(), N));
    }
  } else {
    Dst.insert(DstPreVisit);
  }
}