CallEvent.cpp

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//===- CallEvent.cpp - Wrapper for all function and method calls ----------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
/// \file This file defines CallEvent and its subclasses, which represent path-
/// sensitive instances of different kinds of function and method calls
/// (C, C++, and Objective-C).
//
//===----------------------------------------------------------------------===//
 
#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Attr.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclBase.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/ParentMap.h"
#include "clang/AST/Stmt.h"
#include "clang/AST/Type.h"
#include "clang/Analysis/AnalysisDeclContext.h"
#include "clang/Analysis/CFG.h"
#include "clang/Analysis/CFGStmtMap.h"
#include "clang/Analysis/PathDiagnostic.h"
#include "clang/Analysis/ProgramPoint.h"
#include "clang/Basic/IdentifierTable.h"
#include "clang/Basic/LLVM.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/Specifiers.h"
#include "clang/CrossTU/CrossTranslationUnit.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/DynamicType.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/DynamicTypeInfo.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/ProgramState_Fwd.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SValBuilder.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/SVals.h"
#include "clang/StaticAnalyzer/Core/PathSensitive/Store.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/ImmutableList.h"
#include "llvm/ADT/None.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/PointerIntPair.h"
#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <utility>
 
#define DEBUG_TYPE "static-analyzer-call-event"
 
using namespace clang;
using namespace ento;
 
QualType CallEvent::getResultType() const {
  ASTContext &Ctx = getState()->getStateManager().getContext();
  const Expr *E = getOriginExpr();
  if (!E)
    return Ctx.VoidTy;
  return Ctx.getReferenceQualifiedType(E);
}
 
static bool isCallback(QualType T) {
  // If a parameter is a block or a callback, assume it can modify pointer.
  if (T->isBlockPointerType() ||
      T->isFunctionPointerType() ||
      T->isObjCSelType())
    return true;
 
  // Check if a callback is passed inside a struct (for both, struct passed by
  // reference and by value). Dig just one level into the struct for now.
 
  if (T->isAnyPointerType() || T->isReferenceType())
    T = T->getPointeeType();
 
  if (const RecordType *RT = T->getAsStructureType()) {
    const RecordDecl *RD = RT->getDecl();
    for (const auto *I : RD->fields()) {
      QualType FieldT = I->getType();
      if (FieldT->isBlockPointerType() || FieldT->isFunctionPointerType())
        return true;
    }
  }
  return false;
}
 
static bool isVoidPointerToNonConst(QualType T) {
  if (const auto *PT = T->getAs<PointerType>()) {
    QualType PointeeTy = PT->getPointeeType();
    if (PointeeTy.isConstQualified())
      return false;
    return PointeeTy->isVoidType();
  } else
    return false;
}
 
bool CallEvent::hasNonNullArgumentsWithType(bool (*Condition)(QualType)) const {
  unsigned NumOfArgs = getNumArgs();
 
  // If calling using a function pointer, assume the function does not
  // satisfy the callback.
  // TODO: We could check the types of the arguments here.
  if (!getDecl())
    return false;
 
  unsigned Idx = 0;
  for (CallEvent::param_type_iterator I = param_type_begin(),
                                      E = param_type_end();
       I != E && Idx < NumOfArgs; ++I, ++Idx) {
    // If the parameter is 0, it's harmless.
    if (getArgSVal(Idx).isZeroConstant())
      continue;
 
    if (Condition(*I))
      return true;
  }
  return false;
}
 
bool CallEvent::hasNonZeroCallbackArg() const {
  return hasNonNullArgumentsWithType(isCallback);
}
 
bool CallEvent::hasVoidPointerToNonConstArg() const {
  return hasNonNullArgumentsWithType(isVoidPointerToNonConst);
}
 
bool CallEvent::isGlobalCFunction(StringRef FunctionName) const {
  const auto *FD = dyn_cast_or_null<FunctionDecl>(getDecl());
  if (!FD)
    return false;
 
  return CheckerContext::isCLibraryFunction(FD, FunctionName);
}
 
AnalysisDeclContext *CallEvent::getCalleeAnalysisDeclContext() const {
  const Decl *D = getDecl();
  if (!D)
    return nullptr;
 
  AnalysisDeclContext *ADC =
      LCtx->getAnalysisDeclContext()->getManager()->getContext(D);
 
  return ADC;
}
 
const StackFrameContext *
CallEvent::getCalleeStackFrame(unsigned BlockCount) const {
  AnalysisDeclContext *ADC = getCalleeAnalysisDeclContext();
  if (!ADC)
    return nullptr;
 
  const Expr *E = getOriginExpr();
  if (!E)
    return nullptr;
 
  // Recover CFG block via reverse lookup.
  // TODO: If we were to keep CFG element information as part of the CallEvent
  // instead of doing this reverse lookup, we would be able to build the stack
  // frame for non-expression-based calls, and also we wouldn't need the reverse
  // lookup.
  CFGStmtMap *Map = LCtx->getAnalysisDeclContext()->getCFGStmtMap();
  const CFGBlock *B = Map->getBlock(E);
  assert(B);
 
  // Also recover CFG index by scanning the CFG block.
  unsigned Idx = 0, Sz = B->size();
  for (; Idx < Sz; ++Idx)
    if (auto StmtElem = (*B)[Idx].getAs<CFGStmt>())
      if (StmtElem->getStmt() == E)
        break;
  assert(Idx < Sz);
 
  return ADC->getManager()->getStackFrame(ADC, LCtx, E, B, BlockCount, Idx);
}
 
const ParamVarRegion
*CallEvent::getParameterLocation(unsigned Index, unsigned BlockCount) const {
  const StackFrameContext *SFC = getCalleeStackFrame(BlockCount);
  // We cannot construct a VarRegion without a stack frame.
  if (!SFC)
    return nullptr;
 
  const ParamVarRegion *PVR =
    State->getStateManager().getRegionManager().getParamVarRegion(
        getOriginExpr(), Index, SFC);
  return PVR;
}
 
/// Returns true if a type is a pointer-to-const or reference-to-const
/// with no further indirection.
static bool isPointerToConst(QualType Ty) {
  QualType PointeeTy = Ty->getPointeeType();
  if (PointeeTy == QualType())
    return false;
  if (!PointeeTy.isConstQualified())
    return false;
  if (PointeeTy->isAnyPointerType())
    return false;
  return true;
}
 
// Try to retrieve the function declaration and find the function parameter
// types which are pointers/references to a non-pointer const.
// We will not invalidate the corresponding argument regions.
static void findPtrToConstParams(llvm::SmallSet<unsigned, 4> &PreserveArgs,
                                 const CallEvent &Call) {
  unsigned Idx = 0;
  for (CallEvent::param_type_iterator I = Call.param_type_begin(),
                                      E = Call.param_type_end();
       I != E; ++I, ++Idx) {
    if (isPointerToConst(*I))
      PreserveArgs.insert(Idx);
  }
}
 
ProgramStateRef CallEvent::invalidateRegions(unsigned BlockCount,
                                             ProgramStateRef Orig) const {
  ProgramStateRef Result = (Orig ? Orig : getState());
 
  // Don't invalidate anything if the callee is marked pure/const.
  if (const Decl *callee = getDecl())
    if (callee->hasAttr<PureAttr>() || callee->hasAttr<ConstAttr>())
      return Result;
 
  SmallVector<SVal, 8> ValuesToInvalidate;
  RegionAndSymbolInvalidationTraits ETraits;
 
  getExtraInvalidatedValues(ValuesToInvalidate, &ETraits);
 
  // Indexes of arguments whose values will be preserved by the call.
  llvm::SmallSet<unsigned, 4> PreserveArgs;
  if (!argumentsMayEscape())
    findPtrToConstParams(PreserveArgs, *this);
 
  for (unsigned Idx = 0, Count = getNumArgs(); Idx != Count; ++Idx) {
    // Mark this region for invalidation.  We batch invalidate regions
    // below for efficiency.
    if (PreserveArgs.count(Idx))
      if (const MemRegion *MR = getArgSVal(Idx).getAsRegion())
        ETraits.setTrait(MR->getBaseRegion(),
                        RegionAndSymbolInvalidationTraits::TK_PreserveContents);
        // TODO: Factor this out + handle the lower level const pointers.
 
    ValuesToInvalidate.push_back(getArgSVal(Idx));
 
    // If a function accepts an object by argument (which would of course be a
    // temporary that isn't lifetime-extended), invalidate the object itself,
    // not only other objects reachable from it. This is necessary because the
    // destructor has access to the temporary object after the call.
    // TODO: Support placement arguments once we start
    // constructing them directly.
    // TODO: This is unnecessary when there's no destructor, but that's
    // currently hard to figure out.
    if (getKind() != CE_CXXAllocator)
      if (isArgumentConstructedDirectly(Idx))
        if (auto AdjIdx = getAdjustedParameterIndex(Idx))
          if (const TypedValueRegion *TVR =
                  getParameterLocation(*AdjIdx, BlockCount))
            ValuesToInvalidate.push_back(loc::MemRegionVal(TVR));
  }
 
  // Invalidate designated regions using the batch invalidation API.
  // NOTE: Even if RegionsToInvalidate is empty, we may still invalidate
  //  global variables.
  return Result->invalidateRegions(ValuesToInvalidate, getOriginExpr(),
                                   BlockCount, getLocationContext(),
                                   /*CausedByPointerEscape*/ true,
                                   /*Symbols=*/nullptr, this, &ETraits);
}
 
ProgramPoint CallEvent::getProgramPoint(bool IsPreVisit,
                                        const ProgramPointTag *Tag) const {
  if (const Expr *E = getOriginExpr()) {
    if (IsPreVisit)
      return PreStmt(E, getLocationContext(), Tag);
    return PostStmt(E, getLocationContext(), Tag);
  }
 
  const Decl *D = getDecl();
  assert(D && "Cannot get a program point without a statement or decl");
 
  SourceLocation Loc = getSourceRange().getBegin();
  if (IsPreVisit)
    return PreImplicitCall(D, Loc, getLocationContext(), Tag);
  return PostImplicitCall(D, Loc, getLocationContext(), Tag);
}
 
SVal CallEvent::getArgSVal(unsigned Index) const {
  const Expr *ArgE = getArgExpr(Index);
  if (!ArgE)
    return UnknownVal();
  return getSVal(ArgE);
}
 
SourceRange CallEvent::getArgSourceRange(unsigned Index) const {
  const Expr *ArgE = getArgExpr(Index);
  if (!ArgE)
    return {};
  return ArgE->getSourceRange();
}
 
SVal CallEvent::getReturnValue() const {
  const Expr *E = getOriginExpr();
  if (!E)
    return UndefinedVal();
  return getSVal(E);
}
 
LLVM_DUMP_METHOD void CallEvent::dump() const { dump(llvm::errs()); }
 
void CallEvent::dump(raw_ostream &Out) const {
  ASTContext &Ctx = getState()->getStateManager().getContext();
  if (const Expr *E = getOriginExpr()) {
    E->printPretty(Out, nullptr, Ctx.getPrintingPolicy());
    return;
  }
 
  if (const Decl *D = getDecl()) {
    Out << "Call to ";
    D->print(Out, Ctx.getPrintingPolicy());
    return;
  }
 
  Out << "Unknown call (type " << getKindAsString() << ")";
}
 
bool CallEvent::isCallStmt(const Stmt *S) {
  return isa<CallExpr, ObjCMessageExpr, CXXConstructExpr, CXXNewExpr>(S);
}
 
QualType CallEvent::getDeclaredResultType(const Decl *D) {
  assert(D);
  if (const auto *FD = dyn_cast<FunctionDecl>(D))
    return FD->getReturnType();
  if (const auto *MD = dyn_cast<ObjCMethodDecl>(D))
    return MD->getReturnType();
  if (const auto *BD = dyn_cast<BlockDecl>(D)) {
    // Blocks are difficult because the return type may not be stored in the
    // BlockDecl itself. The AST should probably be enhanced, but for now we
    // just do what we can.
    // If the block is declared without an explicit argument list, the
    // signature-as-written just includes the return type, not the entire
    // function type.
    // FIXME: All blocks should have signatures-as-written, even if the return
    // type is inferred. (That's signified with a dependent result type.)
    if (const TypeSourceInfo *TSI = BD->getSignatureAsWritten()) {
      QualType Ty = TSI->getType();
      if (const FunctionType *FT = Ty->getAs<FunctionType>())
        Ty = FT->getReturnType();
      if (!Ty->isDependentType())
        return Ty;
    }
 
    return {};
  }
 
  llvm_unreachable("unknown callable kind");
}
 
bool CallEvent::isVariadic(const Decl *D) {
  assert(D);
 
  if (const auto *FD = dyn_cast<FunctionDecl>(D))
    return FD->isVariadic();
  if (const auto *MD = dyn_cast<ObjCMethodDecl>(D))
    return MD->isVariadic();
  if (const auto *BD = dyn_cast<BlockDecl>(D))
    return BD->isVariadic();
 
  llvm_unreachable("unknown callable kind");
}
 
static bool isTransparentUnion(QualType T) {
  const RecordType *UT = T->getAsUnionType();
  return UT && UT->getDecl()->hasAttr<TransparentUnionAttr>();
}
 
// In some cases, symbolic cases should be transformed before we associate
// them with parameters.  This function incapsulates such cases.
static SVal processArgument(SVal Value, const Expr *ArgumentExpr,
                            const ParmVarDecl *Parameter, SValBuilder &SVB) {
  QualType ParamType = Parameter->getType();
  QualType ArgumentType = ArgumentExpr->getType();
 
  // Transparent unions allow users to easily convert values of union field
  // types into union-typed objects.
  //
  // Also, more importantly, they allow users to define functions with different
  // different parameter types, substituting types matching transparent union
  // field types with the union type itself.
  //
  // Here, we check specifically for latter cases and prevent binding
  // field-typed values to union-typed regions.
  if (isTransparentUnion(ParamType) &&
      // Let's check that we indeed trying to bind different types.
      !isTransparentUnion(ArgumentType)) {
    BasicValueFactory &BVF = SVB.getBasicValueFactory();
 
    llvm::ImmutableList<SVal> CompoundSVals = BVF.getEmptySValList();
    CompoundSVals = BVF.prependSVal(Value, CompoundSVals);
 
    // Wrap it with compound value.
    return SVB.makeCompoundVal(ParamType, CompoundSVals);
  }
 
  return Value;
}
 
static void addParameterValuesToBindings(const StackFrameContext *CalleeCtx,
                                         CallEvent::BindingsTy &Bindings,
                                         SValBuilder &SVB,
                                         const CallEvent &Call,
                                         ArrayRef<ParmVarDecl*> parameters) {
  MemRegionManager &MRMgr = SVB.getRegionManager();
 
  // If the function has fewer parameters than the call has arguments, we simply
  // do not bind any values to them.
  unsigned NumArgs = Call.getNumArgs();
  unsigned Idx = 0;
  ArrayRef<ParmVarDecl*>::iterator I = parameters.begin(), E = parameters.end();
  for (; I != E && Idx < NumArgs; ++I, ++Idx) {
    assert(*I && "Formal parameter has no decl?");
 
    // TODO: Support allocator calls.
    if (Call.getKind() != CE_CXXAllocator)
      if (Call.isArgumentConstructedDirectly(Call.getASTArgumentIndex(Idx)))
        continue;
 
    // TODO: Allocators should receive the correct size and possibly alignment,
    // determined in compile-time but not represented as arg-expressions,
    // which makes getArgSVal() fail and return UnknownVal.
    SVal ArgVal = Call.getArgSVal(Idx);
    const Expr *ArgExpr = Call.getArgExpr(Idx);
    if (!ArgVal.isUnknown()) {
      Loc ParamLoc = SVB.makeLoc(
          MRMgr.getParamVarRegion(Call.getOriginExpr(), Idx, CalleeCtx));
      Bindings.push_back(
          std::make_pair(ParamLoc, processArgument(ArgVal, ArgExpr, *I, SVB)));
    }
  }
 
  // FIXME: Variadic arguments are not handled at all right now.
}
 
const ConstructionContext *CallEvent::getConstructionContext() const {
  const StackFrameContext *StackFrame = getCalleeStackFrame(0);
  if (!StackFrame)
    return nullptr;
 
  const CFGElement Element = StackFrame->getCallSiteCFGElement();
  if (const auto Ctor = Element.getAs<CFGConstructor>()) {
    return Ctor->getConstructionContext();
  }
 
  if (const auto RecCall = Element.getAs<CFGCXXRecordTypedCall>()) {
    return RecCall->getConstructionContext();
  }
 
  return nullptr;
}
 
Optional<SVal>
CallEvent::getReturnValueUnderConstruction() const {
  const auto *CC = getConstructionContext();
  if (!CC)
    return None;
 
  EvalCallOptions CallOpts;
  ExprEngine &Engine = getState()->getStateManager().getOwningEngine();
  SVal RetVal =
    Engine.computeObjectUnderConstruction(getOriginExpr(), getState(),
                                          getLocationContext(), CC, CallOpts);
  return RetVal;
}
 
ArrayRef<ParmVarDecl*> AnyFunctionCall::parameters() const {
  const FunctionDecl *D = getDecl();
  if (!D)
    return None;
  return D->parameters();
}
 
RuntimeDefinition AnyFunctionCall::getRuntimeDefinition() const {
  const FunctionDecl *FD = getDecl();
  if (!FD)
    return {};
 
  // Note that the AnalysisDeclContext will have the FunctionDecl with
  // the definition (if one exists).
  AnalysisDeclContext *AD =
    getLocationContext()->getAnalysisDeclContext()->
    getManager()->getContext(FD);
  bool IsAutosynthesized;
  Stmt* Body = AD->getBody(IsAutosynthesized);
  LLVM_DEBUG({
    if (IsAutosynthesized)
      llvm::dbgs() << "Using autosynthesized body for " << FD->getName()
                   << "\n";
  });
  if (Body) {
    const Decl* Decl = AD->getDecl();
    return RuntimeDefinition(Decl);
  }
 
  ExprEngine &Engine = getState()->getStateManager().getOwningEngine();
  AnalyzerOptions &Opts = Engine.getAnalysisManager().options;
 
  // Try to get CTU definition only if CTUDir is provided.
  if (!Opts.IsNaiveCTUEnabled)
    return {};
 
  cross_tu::CrossTranslationUnitContext &CTUCtx =
      *Engine.getCrossTranslationUnitContext();
  llvm::Expected<const FunctionDecl *> CTUDeclOrError =
      CTUCtx.getCrossTUDefinition(FD, Opts.CTUDir, Opts.CTUIndexName,
                                  Opts.DisplayCTUProgress);
 
  if (!CTUDeclOrError) {
    handleAllErrors(CTUDeclOrError.takeError(),
                    [&](const cross_tu::IndexError &IE) {
                      CTUCtx.emitCrossTUDiagnostics(IE);
                    });
    return {};
  }
 
  return RuntimeDefinition(*CTUDeclOrError);
}
 
void AnyFunctionCall::getInitialStackFrameContents(
                                        const StackFrameContext *CalleeCtx,
                                        BindingsTy &Bindings) const {
  const auto *D = cast<FunctionDecl>(CalleeCtx->getDecl());
  SValBuilder &SVB = getState()->getStateManager().getSValBuilder();
  addParameterValuesToBindings(CalleeCtx, Bindings, SVB, *this,
                               D->parameters());
}
 
bool AnyFunctionCall::argumentsMayEscape() const {
  if (CallEvent::argumentsMayEscape() || hasVoidPointerToNonConstArg())
    return true;
 
  const FunctionDecl *D = getDecl();
  if (!D)
    return true;
 
  const IdentifierInfo *II = D->getIdentifier();
  if (!II)
    return false;
 
  // This set of "escaping" APIs is
 
  // - 'int pthread_setspecific(ptheread_key k, const void *)' stores a
  //   value into thread local storage. The value can later be retrieved with
  //   'void *ptheread_getspecific(pthread_key)'. So even thought the
  //   parameter is 'const void *', the region escapes through the call.
  if (II->isStr("pthread_setspecific"))
    return true;
 
  // - xpc_connection_set_context stores a value which can be retrieved later
  //   with xpc_connection_get_context.
  if (II->isStr("xpc_connection_set_context"))
    return true;
 
  // - funopen - sets a buffer for future IO calls.
  if (II->isStr("funopen"))
    return true;
 
  // - __cxa_demangle - can reallocate memory and can return the pointer to
  // the input buffer.
  if (II->isStr("__cxa_demangle"))
    return true;
 
  StringRef FName = II->getName();
 
  // - CoreFoundation functions that end with "NoCopy" can free a passed-in
  //   buffer even if it is const.
  if (FName.endswith("NoCopy"))
    return true;
 
  // - NSXXInsertXX, for example NSMapInsertIfAbsent, since they can
  //   be deallocated by NSMapRemove.
  if (FName.startswith("NS") && FName.contains("Insert"))
    return true;
 
  // - Many CF containers allow objects to escape through custom
  //   allocators/deallocators upon container construction. (PR12101)
  if (FName.startswith("CF") || FName.startswith("CG")) {
    return StrInStrNoCase(FName, "InsertValue")  != StringRef::npos ||
           StrInStrNoCase(FName, "AddValue")     != StringRef::npos ||
           StrInStrNoCase(FName, "SetValue")     != StringRef::npos ||
           StrInStrNoCase(FName, "WithData")     != StringRef::npos ||
           StrInStrNoCase(FName, "AppendValue")  != StringRef::npos ||
           StrInStrNoCase(FName, "SetAttribute") != StringRef::npos;
  }
 
  return false;
}
 
const FunctionDecl *SimpleFunctionCall::getDecl() const {
  const FunctionDecl *D = getOriginExpr()->getDirectCallee();
  if (D)
    return D;
 
  return getSVal(getOriginExpr()->getCallee()).getAsFunctionDecl();
}
 
const FunctionDecl *CXXInstanceCall::getDecl() const {
  const auto *CE = cast_or_null<CallExpr>(getOriginExpr());
  if (!CE)
    return AnyFunctionCall::getDecl();
 
  const FunctionDecl *D = CE->getDirectCallee();
  if (D)
    return D;
 
  return getSVal(CE->getCallee()).getAsFunctionDecl();
}
 
void CXXInstanceCall::getExtraInvalidatedValues(
    ValueList &Values, RegionAndSymbolInvalidationTraits *ETraits) const {
  SVal ThisVal = getCXXThisVal();
  Values.push_back(ThisVal);
 
  // Don't invalidate if the method is const and there are no mutable fields.
  if (const auto *D = cast_or_null<CXXMethodDecl>(getDecl())) {
    if (!D->isConst())
      return;
    // Get the record decl for the class of 'This'. D->getParent() may return a
    // base class decl, rather than the class of the instance which needs to be
    // checked for mutable fields.
    // TODO: We might as well look at the dynamic type of the object.
    const Expr *Ex = getCXXThisExpr()->IgnoreParenBaseCasts();
    QualType T = Ex->getType();
    if (T->isPointerType()) // Arrow or implicit-this syntax?
      T = T->getPointeeType();
    const CXXRecordDecl *ParentRecord = T->getAsCXXRecordDecl();
    assert(ParentRecord);
    if (ParentRecord->hasMutableFields())
      return;
    // Preserve CXXThis.
    const MemRegion *ThisRegion = ThisVal.getAsRegion();
    if (!ThisRegion)
      return;
 
    ETraits->setTrait(ThisRegion->getBaseRegion(),
                      RegionAndSymbolInvalidationTraits::TK_PreserveContents);
  }
}
 
SVal CXXInstanceCall::getCXXThisVal() const {
  const Expr *Base = getCXXThisExpr();
  // FIXME: This doesn't handle an overloaded ->* operator.
  if (!Base)
    return UnknownVal();
 
  SVal ThisVal = getSVal(Base);
  assert(ThisVal.isUnknownOrUndef() || ThisVal.getAs<Loc>());
  return ThisVal;
}
 
RuntimeDefinition CXXInstanceCall::getRuntimeDefinition() const {
  // Do we have a decl at all?
  const Decl *D = getDecl();
  if (!D)
    return {};
 
  // If the method is non-virtual, we know we can inline it.
  const auto *MD = cast<CXXMethodDecl>(D);
  if (!MD->isVirtual())
    return AnyFunctionCall::getRuntimeDefinition();
 
  // Do we know the implicit 'this' object being called?
  const MemRegion *R = getCXXThisVal().getAsRegion();
  if (!R)
    return {};
 
  // Do we know anything about the type of 'this'?
  DynamicTypeInfo DynType = getDynamicTypeInfo(getState(), R);
  if (!DynType.isValid())
    return {};
 
  // Is the type a C++ class? (This is mostly a defensive check.)
  QualType RegionType = DynType.getType()->getPointeeType();
  assert(!RegionType.isNull() && "DynamicTypeInfo should always be a pointer.");
 
  const CXXRecordDecl *RD = RegionType->getAsCXXRecordDecl();
  if (!RD || !RD->hasDefinition())
    return {};
 
  // Find the decl for this method in that class.
  const CXXMethodDecl *Result = MD->getCorrespondingMethodInClass(RD, true);
  if (!Result) {
    // We might not even get the original statically-resolved method due to
    // some particularly nasty casting (e.g. casts to sister classes).
    // However, we should at least be able to search up and down our own class
    // hierarchy, and some real bugs have been caught by checking this.
    assert(!RD->isDerivedFrom(MD->getParent()) && "Couldn't find known method");
 
    // FIXME: This is checking that our DynamicTypeInfo is at least as good as
    // the static type. However, because we currently don't update
    // DynamicTypeInfo when an object is cast, we can't actually be sure the
    // DynamicTypeInfo is up to date. This assert should be re-enabled once
    // this is fixed. <rdar://problem/12287087>
    //assert(!MD->getParent()->isDerivedFrom(RD) && "Bad DynamicTypeInfo");
 
    return {};
  }
 
  // Does the decl that we found have an implementation?
  const FunctionDecl *Definition;
  if (!Result->hasBody(Definition)) {
    if (!DynType.canBeASubClass())
      return AnyFunctionCall::getRuntimeDefinition();
    return {};
  }
 
  // We found a definition. If we're not sure that this devirtualization is
  // actually what will happen at runtime, make sure to provide the region so
  // that ExprEngine can decide what to do with it.
  if (DynType.canBeASubClass())
    return RuntimeDefinition(Definition, R->StripCasts());
  return RuntimeDefinition(Definition, /*DispatchRegion=*/nullptr);
}
 
void CXXInstanceCall::getInitialStackFrameContents(
                                            const StackFrameContext *CalleeCtx,
                                            BindingsTy &Bindings) const {
  AnyFunctionCall::getInitialStackFrameContents(CalleeCtx, Bindings);
 
  // Handle the binding of 'this' in the new stack frame.
  SVal ThisVal = getCXXThisVal();
  if (!ThisVal.isUnknown()) {
    ProgramStateManager &StateMgr = getState()->getStateManager();
    SValBuilder &SVB = StateMgr.getSValBuilder();
 
    const auto *MD = cast<CXXMethodDecl>(CalleeCtx->getDecl());
    Loc ThisLoc = SVB.getCXXThis(MD, CalleeCtx);
 
    // If we devirtualized to a different member function, we need to make sure
    // we have the proper layering of CXXBaseObjectRegions.
    if (MD->getCanonicalDecl() != getDecl()->getCanonicalDecl()) {
      ASTContext &Ctx = SVB.getContext();
      const CXXRecordDecl *Class = MD->getParent();
      QualType Ty = Ctx.getPointerType(Ctx.getRecordType(Class));
 
      // FIXME: CallEvent maybe shouldn't be directly accessing StoreManager.
      bool Failed;
      ThisVal = StateMgr.getStoreManager().attemptDownCast(ThisVal, Ty, Failed);
      if (Failed) {
        // We might have suffered some sort of placement new earlier, so
        // we're constructing in a completely unexpected storage.
        // Fall back to a generic pointer cast for this-value.
        const CXXMethodDecl *StaticMD = cast<CXXMethodDecl>(getDecl());
        const CXXRecordDecl *StaticClass = StaticMD->getParent();
        QualType StaticTy = Ctx.getPointerType(Ctx.getRecordType(StaticClass));
        ThisVal = SVB.evalCast(ThisVal, Ty, StaticTy);
      }
    }
 
    if (!ThisVal.isUnknown())
      Bindings.push_back(std::make_pair(ThisLoc, ThisVal));
  }
}
 
const Expr *CXXMemberCall::getCXXThisExpr() const {
  return getOriginExpr()->getImplicitObjectArgument();
}
 
RuntimeDefinition CXXMemberCall::getRuntimeDefinition() const {
  // C++11 [expr.call]p1: ...If the selected function is non-virtual, or if the
  // id-expression in the class member access expression is a qualified-id,
  // that function is called. Otherwise, its final overrider in the dynamic type
  // of the object expression is called.
  if (const auto *ME = dyn_cast<MemberExpr>(getOriginExpr()->getCallee()))
    if (ME->hasQualifier())
      return AnyFunctionCall::getRuntimeDefinition();
 
  return CXXInstanceCall::getRuntimeDefinition();
}
 
const Expr *CXXMemberOperatorCall::getCXXThisExpr() const {
  return getOriginExpr()->getArg(0);
}
 
const BlockDataRegion *BlockCall::getBlockRegion() const {
  const Expr *Callee = getOriginExpr()->getCallee();
  const MemRegion *DataReg = getSVal(Callee).getAsRegion();
 
  return dyn_cast_or_null<BlockDataRegion>(DataReg);
}
 
ArrayRef<ParmVarDecl*> BlockCall::parameters() const {
  const BlockDecl *D = getDecl();
  if (!D)
    return None;
  return D->parameters();
}
 
void BlockCall::getExtraInvalidatedValues(ValueList &Values,
                  RegionAndSymbolInvalidationTraits *ETraits) const {
  // FIXME: This also needs to invalidate captured globals.
  if (const MemRegion *R = getBlockRegion())
    Values.push_back(loc::MemRegionVal(R));
}
 
void BlockCall::getInitialStackFrameContents(const StackFrameContext *CalleeCtx,
                                             BindingsTy &Bindings) const {
  SValBuilder &SVB = getState()->getStateManager().getSValBuilder();
  ArrayRef<ParmVarDecl*> Params;
  if (isConversionFromLambda()) {
    auto *LambdaOperatorDecl = cast<CXXMethodDecl>(CalleeCtx->getDecl());
    Params = LambdaOperatorDecl->parameters();
 
    // For blocks converted from a C++ lambda, the callee declaration is the
    // operator() method on the lambda so we bind "this" to
    // the lambda captured by the block.
    const VarRegion *CapturedLambdaRegion = getRegionStoringCapturedLambda();
    SVal ThisVal = loc::MemRegionVal(CapturedLambdaRegion);
    Loc ThisLoc = SVB.getCXXThis(LambdaOperatorDecl, CalleeCtx);
    Bindings.push_back(std::make_pair(ThisLoc, ThisVal));
  } else {
    Params = cast<BlockDecl>(CalleeCtx->getDecl())->parameters();
  }
 
  addParameterValuesToBindings(CalleeCtx, Bindings, SVB, *this,
                               Params);
}
 
SVal AnyCXXConstructorCall::getCXXThisVal() const {
  if (Data)
    return loc::MemRegionVal(static_cast<const MemRegion *>(Data));
  return UnknownVal();
}
 
void AnyCXXConstructorCall::getExtraInvalidatedValues(ValueList &Values,
                           RegionAndSymbolInvalidationTraits *ETraits) const {
  SVal V = getCXXThisVal();
  if (SymbolRef Sym = V.getAsSymbol(true))
    ETraits->setTrait(Sym,
                      RegionAndSymbolInvalidationTraits::TK_SuppressEscape);
  Values.push_back(V);
}
 
void AnyCXXConstructorCall::getInitialStackFrameContents(
                                             const StackFrameContext *CalleeCtx,
                                             BindingsTy &Bindings) const {
  AnyFunctionCall::getInitialStackFrameContents(CalleeCtx, Bindings);
 
  SVal ThisVal = getCXXThisVal();
  if (!ThisVal.isUnknown()) {
    SValBuilder &SVB = getState()->getStateManager().getSValBuilder();
    const auto *MD = cast<CXXMethodDecl>(CalleeCtx->getDecl());
    Loc ThisLoc = SVB.getCXXThis(MD, CalleeCtx);
    Bindings.push_back(std::make_pair(ThisLoc, ThisVal));
  }
}
 
const StackFrameContext *
CXXInheritedConstructorCall::getInheritingStackFrame() const {
  const StackFrameContext *SFC = getLocationContext()->getStackFrame();
  while (isa<CXXInheritedCtorInitExpr>(SFC->getCallSite()))
    SFC = SFC->getParent()->getStackFrame();
  return SFC;
}
 
SVal CXXDestructorCall::getCXXThisVal() const {
  if (Data)
    return loc::MemRegionVal(DtorDataTy::getFromOpaqueValue(Data).getPointer());
  return UnknownVal();
}
 
RuntimeDefinition CXXDestructorCall::getRuntimeDefinition() const {
  // Base destructors are always called non-virtually.
  // Skip CXXInstanceCall's devirtualization logic in this case.
  if (isBaseDestructor())
    return AnyFunctionCall::getRuntimeDefinition();
 
  return CXXInstanceCall::getRuntimeDefinition();
}
 
ArrayRef<ParmVarDecl*> ObjCMethodCall::parameters() const {
  const ObjCMethodDecl *D = getDecl();
  if (!D)
    return None;
  return D->parameters();
}
 
void ObjCMethodCall::getExtraInvalidatedValues(
    ValueList &Values, RegionAndSymbolInvalidationTraits *ETraits) const {
 
  // If the method call is a setter for property known to be backed by
  // an instance variable, don't invalidate the entire receiver, just
  // the storage for that instance variable.
  if (const ObjCPropertyDecl *PropDecl = getAccessedProperty()) {
    if (const ObjCIvarDecl *PropIvar = PropDecl->getPropertyIvarDecl()) {
      SVal IvarLVal = getState()->getLValue(PropIvar, getReceiverSVal());
      if (const MemRegion *IvarRegion = IvarLVal.getAsRegion()) {
        ETraits->setTrait(
          IvarRegion,
          RegionAndSymbolInvalidationTraits::TK_DoNotInvalidateSuperRegion);
        ETraits->setTrait(
          IvarRegion,
          RegionAndSymbolInvalidationTraits::TK_SuppressEscape);
        Values.push_back(IvarLVal);
      }
      return;
    }
  }
 
  Values.push_back(getReceiverSVal());
}
 
SVal ObjCMethodCall::getReceiverSVal() const {
  // FIXME: Is this the best way to handle class receivers?
  if (!isInstanceMessage())
    return UnknownVal();
 
  if (const Expr *RecE = getOriginExpr()->getInstanceReceiver())
    return getSVal(RecE);
 
  // An instance message with no expression means we are sending to super.
  // In this case the object reference is the same as 'self'.
  assert(getOriginExpr()->getReceiverKind() == ObjCMessageExpr::SuperInstance);
  SVal SelfVal = getState()->getSelfSVal(getLocationContext());
  assert(SelfVal.isValid() && "Calling super but not in ObjC method");
  return SelfVal;
}
 
bool ObjCMethodCall::isReceiverSelfOrSuper() const {
  if (getOriginExpr()->getReceiverKind() == ObjCMessageExpr::SuperInstance ||
      getOriginExpr()->getReceiverKind() == ObjCMessageExpr::SuperClass)
      return true;
 
  if (!isInstanceMessage())
    return false;
 
  SVal RecVal = getSVal(getOriginExpr()->getInstanceReceiver());
  SVal SelfVal = getState()->getSelfSVal(getLocationContext());
 
  return (RecVal == SelfVal);
}
 
SourceRange ObjCMethodCall::getSourceRange() const {
  switch (getMessageKind()) {
  case OCM_Message:
    return getOriginExpr()->getSourceRange();
  case OCM_PropertyAccess:
  case OCM_Subscript:
    return getContainingPseudoObjectExpr()->getSourceRange();
  }
  llvm_unreachable("unknown message kind");
}
 
using ObjCMessageDataTy = llvm::PointerIntPair<const PseudoObjectExpr *, 2>;
 
const PseudoObjectExpr *ObjCMethodCall::getContainingPseudoObjectExpr() const {
  assert(Data && "Lazy lookup not yet performed.");
  assert(getMessageKind() != OCM_Message && "Explicit message send.");
  return ObjCMessageDataTy::getFromOpaqueValue(Data).getPointer();
}
 
static const Expr *
getSyntacticFromForPseudoObjectExpr(const PseudoObjectExpr *POE) {
  const Expr *Syntactic = POE->getSyntacticForm()->IgnoreParens();
 
  // This handles the funny case of assigning to the result of a getter.
  // This can happen if the getter returns a non-const reference.
  if (const auto *BO = dyn_cast<BinaryOperator>(Syntactic))
    Syntactic = BO->getLHS()->IgnoreParens();
 
  return Syntactic;
}
 
ObjCMessageKind ObjCMethodCall::getMessageKind() const {
  if (!Data) {
    // Find the parent, ignoring implicit casts.
    const ParentMap &PM = getLocationContext()->getParentMap();
    const Stmt *S = PM.getParentIgnoreParenCasts(getOriginExpr());
 
    // Check if parent is a PseudoObjectExpr.
    if (const auto *POE = dyn_cast_or_null<PseudoObjectExpr>(S)) {
      const Expr *Syntactic = getSyntacticFromForPseudoObjectExpr(POE);
 
      ObjCMessageKind K;
      switch (Syntactic->getStmtClass()) {
      case Stmt::ObjCPropertyRefExprClass:
        K = OCM_PropertyAccess;
        break;
      case Stmt::ObjCSubscriptRefExprClass:
        K = OCM_Subscript;
        break;
      default:
        // FIXME: Can this ever happen?
        K = OCM_Message;
        break;
      }
 
      if (K != OCM_Message) {
        const_cast<ObjCMethodCall *>(this)->Data
          = ObjCMessageDataTy(POE, K).getOpaqueValue();
        assert(getMessageKind() == K);
        return K;
      }
    }
 
    const_cast<ObjCMethodCall *>(this)->Data
      = ObjCMessageDataTy(nullptr, 1).getOpaqueValue();
    assert(getMessageKind() == OCM_Message);
    return OCM_Message;
  }
 
  ObjCMessageDataTy Info = ObjCMessageDataTy::getFromOpaqueValue(Data);
  if (!Info.getPointer())
    return OCM_Message;
  return static_cast<ObjCMessageKind>(Info.getInt());
}
 
const ObjCPropertyDecl *ObjCMethodCall::getAccessedProperty() const {
  // Look for properties accessed with property syntax (foo.bar = ...)
  if (getMessageKind() == OCM_PropertyAccess) {
    const PseudoObjectExpr *POE = getContainingPseudoObjectExpr();
    assert(POE && "Property access without PseudoObjectExpr?");
 
    const Expr *Syntactic = getSyntacticFromForPseudoObjectExpr(POE);
    auto *RefExpr = cast<ObjCPropertyRefExpr>(Syntactic);
 
    if (RefExpr->isExplicitProperty())
      return RefExpr->getExplicitProperty();
  }
 
  // Look for properties accessed with method syntax ([foo setBar:...]).
  const ObjCMethodDecl *MD = getDecl();
  if (!MD || !MD->isPropertyAccessor())
    return nullptr;
 
  // Note: This is potentially quite slow.
  return MD->findPropertyDecl();
}
 
bool ObjCMethodCall::canBeOverridenInSubclass(ObjCInterfaceDecl *IDecl,
                                             Selector Sel) const {
  assert(IDecl);
  AnalysisManager &AMgr =
      getState()->getStateManager().getOwningEngine().getAnalysisManager();
  // If the class interface is declared inside the main file, assume it is not
  // subcassed.
  // TODO: It could actually be subclassed if the subclass is private as well.
  // This is probably very rare.
  SourceLocation InterfLoc = IDecl->getEndOfDefinitionLoc();
  if (InterfLoc.isValid() && AMgr.isInCodeFile(InterfLoc))
    return false;
 
  // Assume that property accessors are not overridden.
  if (getMessageKind() == OCM_PropertyAccess)
    return false;
 
  // We assume that if the method is public (declared outside of main file) or
  // has a parent which publicly declares the method, the method could be
  // overridden in a subclass.
 
  // Find the first declaration in the class hierarchy that declares
  // the selector.
  ObjCMethodDecl *D = nullptr;
  while (true) {
    D = IDecl->lookupMethod(Sel, true);
 
    // Cannot find a public definition.
    if (!D)
      return false;
 
    // If outside the main file,
    if (D->getLocation().isValid() && !AMgr.isInCodeFile(D->getLocation()))
      return true;
 
    if (D->isOverriding()) {
      // Search in the superclass on the next iteration.
      IDecl = D->getClassInterface();
      if (!IDecl)
        return false;
 
      IDecl = IDecl->getSuperClass();
      if (!IDecl)
        return false;
 
      continue;
    }
 
    return false;
  };
 
  llvm_unreachable("The while loop should always terminate.");
}
 
static const ObjCMethodDecl *findDefiningRedecl(const ObjCMethodDecl *MD) {
  if (!MD)
    return MD;
 
  // Find the redeclaration that defines the method.
  if (!MD->hasBody()) {
    for (auto I : MD->redecls())
      if (I->hasBody())
        MD = cast<ObjCMethodDecl>(I);
  }
  return MD;
}
 
struct PrivateMethodKey {
  const ObjCInterfaceDecl *Interface;
  Selector LookupSelector;
  bool IsClassMethod;
};
 
namespace llvm {
template <> struct DenseMapInfo<PrivateMethodKey> {
  using InterfaceInfo = DenseMapInfo<const ObjCInterfaceDecl *>;
  using SelectorInfo = DenseMapInfo<Selector>;
 
  static inline PrivateMethodKey getEmptyKey() {
    return {InterfaceInfo::getEmptyKey(), SelectorInfo::getEmptyKey(), false};
  }
 
  static inline PrivateMethodKey getTombstoneKey() {
    return {InterfaceInfo::getTombstoneKey(), SelectorInfo::getTombstoneKey(),
            true};
  }
 
  static unsigned getHashValue(const PrivateMethodKey &Key) {
    return llvm::hash_combine(
        llvm::hash_code(InterfaceInfo::getHashValue(Key.Interface)),
        llvm::hash_code(SelectorInfo::getHashValue(Key.LookupSelector)),
        Key.IsClassMethod);
  }
 
  static bool isEqual(const PrivateMethodKey &LHS,
                      const PrivateMethodKey &RHS) {
    return InterfaceInfo::isEqual(LHS.Interface, RHS.Interface) &&
           SelectorInfo::isEqual(LHS.LookupSelector, RHS.LookupSelector) &&
           LHS.IsClassMethod == RHS.IsClassMethod;
  }
};
} // end namespace llvm
 
static const ObjCMethodDecl *
lookupRuntimeDefinition(const ObjCInterfaceDecl *Interface,
                        Selector LookupSelector, bool InstanceMethod) {
  // Repeatedly calling lookupPrivateMethod() is expensive, especially
  // when in many cases it returns null.  We cache the results so
  // that repeated queries on the same ObjCIntefaceDecl and Selector
  // don't incur the same cost.  On some test cases, we can see the
  // same query being issued thousands of times.
  //
  // NOTE: This cache is essentially a "global" variable, but it
  // only gets lazily created when we get here.  The value of the
  // cache probably comes from it being global across ExprEngines,
  // where the same queries may get issued.  If we are worried about
  // concurrency, or possibly loading/unloading ASTs, etc., we may
  // need to revisit this someday.  In terms of memory, this table
  // stays around until clang quits, which also may be bad if we
  // need to release memory.
  using PrivateMethodCache =
      llvm::DenseMap<PrivateMethodKey, Optional<const ObjCMethodDecl *>>;
 
  static PrivateMethodCache PMC;
  Optional<const ObjCMethodDecl *> &Val =
      PMC[{Interface, LookupSelector, InstanceMethod}];
 
  // Query lookupPrivateMethod() if the cache does not hit.
  if (!Val.hasValue()) {
    Val = Interface->lookupPrivateMethod(LookupSelector, InstanceMethod);
 
    if (!*Val) {
      // Query 'lookupMethod' as a backup.
      Val = Interface->lookupMethod(LookupSelector, InstanceMethod);
    }
  }
 
  return Val.getValue();
}
 
RuntimeDefinition ObjCMethodCall::getRuntimeDefinition() const {
  const ObjCMessageExpr *E = getOriginExpr();
  assert(E);
  Selector Sel = E->getSelector();
 
  if (E->isInstanceMessage()) {
    // Find the receiver type.
    const ObjCObjectType *ReceiverT = nullptr;
    bool CanBeSubClassed = false;
    bool LookingForInstanceMethod = true;
    QualType SupersType = E->getSuperType();
    const MemRegion *Receiver = nullptr;
 
    if (!SupersType.isNull()) {
      // The receiver is guaranteed to be 'super' in this case.
      // Super always means the type of immediate predecessor to the method
      // where the call occurs.
      ReceiverT = cast<ObjCObjectPointerType>(SupersType)->getObjectType();
    } else {
      Receiver = getReceiverSVal().getAsRegion();
      if (!Receiver)
        return {};
 
      DynamicTypeInfo DTI = getDynamicTypeInfo(getState(), Receiver);
      if (!DTI.isValid()) {
        assert(isa<AllocaRegion>(Receiver) &&
               "Unhandled untyped region class!");
        return {};
      }
 
      QualType DynType = DTI.getType();
      CanBeSubClassed = DTI.canBeASubClass();
 
      const auto *ReceiverDynT =
          dyn_cast<ObjCObjectPointerType>(DynType.getCanonicalType());
 
      if (ReceiverDynT) {
        ReceiverT = ReceiverDynT->getObjectType();
 
        // It can be actually class methods called with Class object as a
        // receiver. This type of messages is treated by the compiler as
        // instance (not class).
        if (ReceiverT->isObjCClass()) {
 
          SVal SelfVal = getState()->getSelfSVal(getLocationContext());
          // For [self classMethod], return compiler visible declaration.
          if (Receiver == SelfVal.getAsRegion()) {
            return RuntimeDefinition(findDefiningRedecl(E->getMethodDecl()));
          }
 
          // Otherwise, let's check if we know something about the type
          // inside of this class object.
          if (SymbolRef ReceiverSym = getReceiverSVal().getAsSymbol()) {
            DynamicTypeInfo DTI =
                getClassObjectDynamicTypeInfo(getState(), ReceiverSym);
            if (DTI.isValid()) {
              // Let's use this type for lookup.
              ReceiverT =
                  cast<ObjCObjectType>(DTI.getType().getCanonicalType());
 
              CanBeSubClassed = DTI.canBeASubClass();
              // And it should be a class method instead.
              LookingForInstanceMethod = false;
            }
          }
        }
 
        if (CanBeSubClassed)
          if (ObjCInterfaceDecl *IDecl = ReceiverT->getInterface())
            // Even if `DynamicTypeInfo` told us that it can be
            // not necessarily this type, but its descendants, we still want
            // to check again if this selector can be actually overridden.
            CanBeSubClassed = canBeOverridenInSubclass(IDecl, Sel);
      }
    }
 
    // Lookup the instance method implementation.
    if (ReceiverT)
      if (ObjCInterfaceDecl *IDecl = ReceiverT->getInterface()) {
        const ObjCMethodDecl *MD =
            lookupRuntimeDefinition(IDecl, Sel, LookingForInstanceMethod);
 
        if (MD && !MD->hasBody())
          MD = MD->getCanonicalDecl();
 
        if (CanBeSubClassed)
          return RuntimeDefinition(MD, Receiver);
        else
          return RuntimeDefinition(MD, nullptr);
      }
  } else {
    // This is a class method.
    // If we have type info for the receiver class, we are calling via
    // class name.
    if (ObjCInterfaceDecl *IDecl = E->getReceiverInterface()) {
      // Find/Return the method implementation.
      return RuntimeDefinition(IDecl->lookupPrivateClassMethod(Sel));
    }
  }
 
  return {};
}
 
bool ObjCMethodCall::argumentsMayEscape() const {
  if (isInSystemHeader() && !isInstanceMessage()) {
    Selector Sel = getSelector();
    if (Sel.getNumArgs() == 1 &&
        Sel.getIdentifierInfoForSlot(0)->isStr("valueWithPointer"))
      return true;
  }
 
  return CallEvent::argumentsMayEscape();
}
 
void ObjCMethodCall::getInitialStackFrameContents(
                                             const StackFrameContext *CalleeCtx,
                                             BindingsTy &Bindings) const {
  const auto *D = cast<ObjCMethodDecl>(CalleeCtx->getDecl());
  SValBuilder &SVB = getState()->getStateManager().getSValBuilder();
  addParameterValuesToBindings(CalleeCtx, Bindings, SVB, *this,
                               D->parameters());
 
  SVal SelfVal = getReceiverSVal();
  if (!SelfVal.isUnknown()) {
    const VarDecl *SelfD = CalleeCtx->getAnalysisDeclContext()->getSelfDecl();
    MemRegionManager &MRMgr = SVB.getRegionManager();
    Loc SelfLoc = SVB.makeLoc(MRMgr.getVarRegion(SelfD, CalleeCtx));
    Bindings.push_back(std::make_pair(SelfLoc, SelfVal));
  }
}
 
CallEventRef<>
CallEventManager::getSimpleCall(const CallExpr *CE, ProgramStateRef State,
                                const LocationContext *LCtx) {
  if (const auto *MCE = dyn_cast<CXXMemberCallExpr>(CE))
    return create<CXXMemberCall>(MCE, State, LCtx);
 
  if (const auto *OpCE = dyn_cast<CXXOperatorCallExpr>(CE)) {
    const FunctionDecl *DirectCallee = OpCE->getDirectCallee();
    if (const auto *MD = dyn_cast<CXXMethodDecl>(DirectCallee))
      if (MD->isInstance())
        return create<CXXMemberOperatorCall>(OpCE, State, LCtx);
 
  } else if (CE->getCallee()->getType()->isBlockPointerType()) {
    return create<BlockCall>(CE, State, LCtx);
  }
 
  // Otherwise, it's a normal function call, static member function call, or
  // something we can't reason about.
  return create<SimpleFunctionCall>(CE, State, LCtx);
}
 
CallEventRef<>
CallEventManager::getCaller(const StackFrameContext *CalleeCtx,
                            ProgramStateRef State) {
  const LocationContext *ParentCtx = CalleeCtx->getParent();
  const LocationContext *CallerCtx = ParentCtx->getStackFrame();
  assert(CallerCtx && "This should not be used for top-level stack frames");
 
  const Stmt *CallSite = CalleeCtx->getCallSite();
 
  if (CallSite) {
    if (CallEventRef<> Out = getCall(CallSite, State, CallerCtx))
      return Out;
 
    SValBuilder &SVB = State->getStateManager().getSValBuilder();
    const auto *Ctor = cast<CXXMethodDecl>(CalleeCtx->getDecl());
    Loc ThisPtr = SVB.getCXXThis(Ctor, CalleeCtx);
    SVal ThisVal = State->getSVal(ThisPtr);
 
    if (const auto *CE = dyn_cast<CXXConstructExpr>(CallSite))
      return getCXXConstructorCall(CE, ThisVal.getAsRegion(), State, CallerCtx);
    else if (const auto *CIE = dyn_cast<CXXInheritedCtorInitExpr>(CallSite))
      return getCXXInheritedConstructorCall(CIE, ThisVal.getAsRegion(), State,
                                            CallerCtx);
    else {
      // All other cases are handled by getCall.
      llvm_unreachable("This is not an inlineable statement");
    }
  }
 
  // Fall back to the CFG. The only thing we haven't handled yet is
  // destructors, though this could change in the future.
  const CFGBlock *B = CalleeCtx->getCallSiteBlock();
  CFGElement E = (*B)[CalleeCtx->getIndex()];
  assert((E.getAs<CFGImplicitDtor>() || E.getAs<CFGTemporaryDtor>()) &&
         "All other CFG elements should have exprs");
 
  SValBuilder &SVB = State->getStateManager().getSValBuilder();
  const auto *Dtor = cast<CXXDestructorDecl>(CalleeCtx->getDecl());
  Loc ThisPtr = SVB.getCXXThis(Dtor, CalleeCtx);
  SVal ThisVal = State->getSVal(ThisPtr);
 
  const Stmt *Trigger;
  if (Optional<CFGAutomaticObjDtor> AutoDtor = E.getAs<CFGAutomaticObjDtor>())
    Trigger = AutoDtor->getTriggerStmt();
  else if (Optional<CFGDeleteDtor> DeleteDtor = E.getAs<CFGDeleteDtor>())
    Trigger = DeleteDtor->getDeleteExpr();
  else
    Trigger = Dtor->getBody();
 
  return getCXXDestructorCall(Dtor, Trigger, ThisVal.getAsRegion(),
                              E.getAs<CFGBaseDtor>().hasValue(), State,
                              CallerCtx);
}
 
CallEventRef<> CallEventManager::getCall(const Stmt *S, ProgramStateRef State,
                                         const LocationContext *LC) {
  if (const auto *CE = dyn_cast<CallExpr>(S)) {
    return getSimpleCall(CE, State, LC);
  } else if (const auto *NE = dyn_cast<CXXNewExpr>(S)) {
    return getCXXAllocatorCall(NE, State, LC);
  } else if (const auto *ME = dyn_cast<ObjCMessageExpr>(S)) {
    return getObjCMethodCall(ME, State, LC);
  } else {
    return nullptr;
  }
}