text: //===--- CallAndMessageChecker.cpp ------------------------------*- 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 defines CallAndMessageChecker, a builtin checker that checks for various
  // errors of call and objc message expressions.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
  #include "clang/AST/ParentMap.h"
  #include "clang/Basic/TargetInfo.h"
  #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
  #include "clang/StaticAnalyzer/Core/Checker.h"
  #include "clang/StaticAnalyzer/Core/CheckerManager.h"
  #include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
  #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/ADT/StringExtras.h"
  #include "llvm/Support/raw_ostream.h"
  
  using namespace clang;
  using namespace ento;
  
  namespace {
  
  class CallAndMessageChecker
    : public Checker< check::PreStmt<CallExpr>,
                      check::PreStmt<CXXDeleteExpr>,
                      check::PreObjCMessage,
                      check::ObjCMessageNil,
                      check::PreCall > {
    mutable std::unique_ptr<BugType> BT_call_null;
    mutable std::unique_ptr<BugType> BT_call_undef;
    mutable std::unique_ptr<BugType> BT_cxx_call_null;
    mutable std::unique_ptr<BugType> BT_cxx_call_undef;
    mutable std::unique_ptr<BugType> BT_call_arg;
    mutable std::unique_ptr<BugType> BT_cxx_delete_undef;
    mutable std::unique_ptr<BugType> BT_msg_undef;
    mutable std::unique_ptr<BugType> BT_objc_prop_undef;
    mutable std::unique_ptr<BugType> BT_objc_subscript_undef;
    mutable std::unique_ptr<BugType> BT_msg_arg;
    mutable std::unique_ptr<BugType> BT_msg_ret;
    mutable std::unique_ptr<BugType> BT_call_few_args;
  
  public:
    DefaultBool Check_CallAndMessageUnInitRefArg;
    CheckerNameRef CheckName_CallAndMessageUnInitRefArg;
  
    void checkPreStmt(const CallExpr *CE, CheckerContext &C) const;
    void checkPreStmt(const CXXDeleteExpr *DE, CheckerContext &C) const;
    void checkPreObjCMessage(const ObjCMethodCall &msg, CheckerContext &C) const;
  
    /// Fill in the return value that results from messaging nil based on the
    /// return type and architecture and diagnose if the return value will be
    /// garbage.
    void checkObjCMessageNil(const ObjCMethodCall &msg, CheckerContext &C) const;
  
    void checkPreCall(const CallEvent &Call, CheckerContext &C) const;
  
  private:
    bool PreVisitProcessArg(CheckerContext &C, SVal V, SourceRange ArgRange,
                            const Expr *ArgEx, int ArgumentNumber,
                            bool CheckUninitFields, const CallEvent &Call,
                            std::unique_ptr<BugType> &BT,
                            const ParmVarDecl *ParamDecl) const;
  
    static void emitBadCall(BugType *BT, CheckerContext &C, const Expr *BadE);
    void emitNilReceiverBug(CheckerContext &C, const ObjCMethodCall &msg,
                            ExplodedNode *N) const;
  
    void HandleNilReceiver(CheckerContext &C,
                           ProgramStateRef state,
                           const ObjCMethodCall &msg) const;
  
    void LazyInit_BT(const char *desc, std::unique_ptr<BugType> &BT) const {
      if (!BT)
        BT.reset(new BuiltinBug(this, desc));
    }
    bool uninitRefOrPointer(CheckerContext &C, const SVal &V,
                            SourceRange ArgRange, const Expr *ArgEx,
                            std::unique_ptr<BugType> &BT,
                            const ParmVarDecl *ParamDecl, const char *BD,
                            int ArgumentNumber) const;
  };
  } // end anonymous namespace
  
  void CallAndMessageChecker::emitBadCall(BugType *BT, CheckerContext &C,
                                          const Expr *BadE) {
    ExplodedNode *N = C.generateErrorNode();
    if (!N)
      return;
  
    auto R = std::make_unique<PathSensitiveBugReport>(*BT, BT->getDescription(), N);
    if (BadE) {
      R->addRange(BadE->getSourceRange());
      if (BadE->isGLValue())
        BadE = bugreporter::getDerefExpr(BadE);
      bugreporter::trackExpressionValue(N, BadE, *R);
    }
    C.emitReport(std::move(R));
  }
  
  static void describeUninitializedArgumentInCall(const CallEvent &Call,
                                                  int ArgumentNumber,
                                                  llvm::raw_svector_ostream &Os) {
    switch (Call.getKind()) {
    case CE_ObjCMessage: {
      const ObjCMethodCall &Msg = cast<ObjCMethodCall>(Call);
      switch (Msg.getMessageKind()) {
      case OCM_Message:
        Os << (ArgumentNumber + 1) << llvm::getOrdinalSuffix(ArgumentNumber + 1)
           << " argument in message expression is an uninitialized value";
        return;
      case OCM_PropertyAccess:
        assert(Msg.isSetter() && "Getters have no args");
        Os << "Argument for property setter is an uninitialized value";
        return;
      case OCM_Subscript:
        if (Msg.isSetter() && (ArgumentNumber == 0))
          Os << "Argument for subscript setter is an uninitialized value";
        else
          Os << "Subscript index is an uninitialized value";
        return;
      }
      llvm_unreachable("Unknown message kind.");
    }
    case CE_Block:
      Os << (ArgumentNumber + 1) << llvm::getOrdinalSuffix(ArgumentNumber + 1)
         << " block call argument is an uninitialized value";
      return;
    default:
      Os << (ArgumentNumber + 1) << llvm::getOrdinalSuffix(ArgumentNumber + 1)
         << " function call argument is an uninitialized value";
      return;
    }
  }
  
  bool CallAndMessageChecker::uninitRefOrPointer(
      CheckerContext &C, const SVal &V, SourceRange ArgRange, const Expr *ArgEx,
      std::unique_ptr<BugType> &BT, const ParmVarDecl *ParamDecl, const char *BD,
      int ArgumentNumber) const {
    if (!Check_CallAndMessageUnInitRefArg)
      return false;
  
    // No parameter declaration available, i.e. variadic function argument.
    if(!ParamDecl)
      return false;
  
    // If parameter is declared as pointer to const in function declaration,
    // then check if corresponding argument in function call is
    // pointing to undefined symbol value (uninitialized memory).
    SmallString<200> Buf;
    llvm::raw_svector_ostream Os(Buf);
  
    if (ParamDecl->getType()->isPointerType()) {
      Os << (ArgumentNumber + 1) << llvm::getOrdinalSuffix(ArgumentNumber + 1)
         << " function call argument is a pointer to uninitialized value";
    } else if (ParamDecl->getType()->isReferenceType()) {
      Os << (ArgumentNumber + 1) << llvm::getOrdinalSuffix(ArgumentNumber + 1)
         << " function call argument is an uninitialized value";
    } else
      return false;
  
    if(!ParamDecl->getType()->getPointeeType().isConstQualified())
      return false;
  
    if (const MemRegion *SValMemRegion = V.getAsRegion()) {
      const ProgramStateRef State = C.getState();
      const SVal PSV = State->getSVal(SValMemRegion, C.getASTContext().CharTy);
      if (PSV.isUndef()) {
        if (ExplodedNode *N = C.generateErrorNode()) {
          LazyInit_BT(BD, BT);
          auto R = std::make_unique<PathSensitiveBugReport>(*BT, Os.str(), N);
          R->addRange(ArgRange);
          if (ArgEx)
            bugreporter::trackExpressionValue(N, ArgEx, *R);
  
          C.emitReport(std::move(R));
        }
        return true;
      }
    }
    return false;
  }
  
  namespace {
  class FindUninitializedField {
  public:
    SmallVector<const FieldDecl *, 10> FieldChain;
  
  private:
    StoreManager &StoreMgr;
    MemRegionManager &MrMgr;
    Store store;
  
  public:
    FindUninitializedField(StoreManager &storeMgr, MemRegionManager &mrMgr,
                           Store s)
        : StoreMgr(storeMgr), MrMgr(mrMgr), store(s) {}
  
    bool Find(const TypedValueRegion *R) {
      QualType T = R->getValueType();
      if (const RecordType *RT = T->getAsStructureType()) {
        const RecordDecl *RD = RT->getDecl()->getDefinition();
        assert(RD && "Referred record has no definition");
        for (const auto *I : RD->fields()) {
          const FieldRegion *FR = MrMgr.getFieldRegion(I, R);
          FieldChain.push_back(I);
          T = I->getType();
          if (T->getAsStructureType()) {
            if (Find(FR))
              return true;
          } else {
            const SVal &V = StoreMgr.getBinding(store, loc::MemRegionVal(FR));
            if (V.isUndef())
              return true;
          }
          FieldChain.pop_back();
        }
      }
  
      return false;
    }
  };
  } // namespace
  
  bool CallAndMessageChecker::PreVisitProcessArg(CheckerContext &C,
                                                 SVal V,
                                                 SourceRange ArgRange,
                                                 const Expr *ArgEx,
                                                 int ArgumentNumber,
                                                 bool CheckUninitFields,
                                                 const CallEvent &Call,
                                                 std::unique_ptr<BugType> &BT,
                                                 const ParmVarDecl *ParamDecl
                                                 ) const {
    const char *BD = "Uninitialized argument value";
  
    if (uninitRefOrPointer(C, V, ArgRange, ArgEx, BT, ParamDecl, BD,
                           ArgumentNumber))
      return true;
  
    if (V.isUndef()) {
      if (ExplodedNode *N = C.generateErrorNode()) {
        LazyInit_BT(BD, BT);
        // Generate a report for this bug.
        SmallString<200> Buf;
        llvm::raw_svector_ostream Os(Buf);
        describeUninitializedArgumentInCall(Call, ArgumentNumber, Os);
        auto R = std::make_unique<PathSensitiveBugReport>(*BT, Os.str(), N);
  
        R->addRange(ArgRange);
        if (ArgEx)
          bugreporter::trackExpressionValue(N, ArgEx, *R);
        C.emitReport(std::move(R));
      }
      return true;
    }
  
    if (!CheckUninitFields)
      return false;
  
    if (auto LV = V.getAs<nonloc::LazyCompoundVal>()) {
      const LazyCompoundValData *D = LV->getCVData();
      FindUninitializedField F(C.getState()->getStateManager().getStoreManager(),
                               C.getSValBuilder().getRegionManager(),
                               D->getStore());
  
      if (F.Find(D->getRegion())) {
        if (ExplodedNode *N = C.generateErrorNode()) {
          LazyInit_BT(BD, BT);
          SmallString<512> Str;
          llvm::raw_svector_ostream os(Str);
          os << "Passed-by-value struct argument contains uninitialized data";
  
          if (F.FieldChain.size() == 1)
            os << " (e.g., field: '" << *F.FieldChain[0] << "')";
          else {
            os << " (e.g., via the field chain: '";
            bool first = true;
            for (SmallVectorImpl<const FieldDecl *>::iterator
                 DI = F.FieldChain.begin(), DE = F.FieldChain.end(); DI!=DE;++DI){
              if (first)
                first = false;
              else
                os << '.';
              os << **DI;
            }
            os << "')";
          }
  
          // Generate a report for this bug.
          auto R = std::make_unique<PathSensitiveBugReport>(*BT, os.str(), N);
          R->addRange(ArgRange);
  
          if (ArgEx)
            bugreporter::trackExpressionValue(N, ArgEx, *R);
          // FIXME: enhance track back for uninitialized value for arbitrary
          // memregions
          C.emitReport(std::move(R));
        }
        return true;
      }
    }
  
    return false;
  }
  
  void CallAndMessageChecker::checkPreStmt(const CallExpr *CE,
                                           CheckerContext &C) const{
  
    const Expr *Callee = CE->getCallee()->IgnoreParens();
    ProgramStateRef State = C.getState();
    const LocationContext *LCtx = C.getLocationContext();
    SVal L = State->getSVal(Callee, LCtx);
  
    if (L.isUndef()) {
      if (!BT_call_undef)
        BT_call_undef.reset(new BuiltinBug(
            this, "Called function pointer is an uninitialized pointer value"));
      emitBadCall(BT_call_undef.get(), C, Callee);
      return;
    }
  
    ProgramStateRef StNonNull, StNull;
    std::tie(StNonNull, StNull) = State->assume(L.castAs<DefinedOrUnknownSVal>());
  
    if (StNull && !StNonNull) {
      if (!BT_call_null)
        BT_call_null.reset(new BuiltinBug(
            this, "Called function pointer is null (null dereference)"));
      emitBadCall(BT_call_null.get(), C, Callee);
      return;
    }
  
    C.addTransition(StNonNull);
  }
  
  void CallAndMessageChecker::checkPreStmt(const CXXDeleteExpr *DE,
                                           CheckerContext &C) const {
  
    SVal Arg = C.getSVal(DE->getArgument());
    if (Arg.isUndef()) {
      StringRef Desc;
      ExplodedNode *N = C.generateErrorNode();
      if (!N)
        return;
      if (!BT_cxx_delete_undef)
        BT_cxx_delete_undef.reset(
            new BuiltinBug(this, "Uninitialized argument value"));
      if (DE->isArrayFormAsWritten())
        Desc = "Argument to 'delete[]' is uninitialized";
      else
        Desc = "Argument to 'delete' is uninitialized";
      BugType *BT = BT_cxx_delete_undef.get();
      auto R = std::make_unique<PathSensitiveBugReport>(*BT, Desc, N);
      bugreporter::trackExpressionValue(N, DE, *R);
      C.emitReport(std::move(R));
      return;
    }
  }
  
  void CallAndMessageChecker::checkPreCall(const CallEvent &Call,
                                           CheckerContext &C) const {
    ProgramStateRef State = C.getState();
  
    // If this is a call to a C++ method, check if the callee is null or
    // undefined.
    if (const CXXInstanceCall *CC = dyn_cast<CXXInstanceCall>(&Call)) {
      SVal V = CC->getCXXThisVal();
      if (V.isUndef()) {
        if (!BT_cxx_call_undef)
          BT_cxx_call_undef.reset(
              new BuiltinBug(this, "Called C++ object pointer is uninitialized"));
        emitBadCall(BT_cxx_call_undef.get(), C, CC->getCXXThisExpr());
        return;
      }
  
      ProgramStateRef StNonNull, StNull;
      std::tie(StNonNull, StNull) =
          State->assume(V.castAs<DefinedOrUnknownSVal>());
  
      if (StNull && !StNonNull) {
        if (!BT_cxx_call_null)
          BT_cxx_call_null.reset(
              new BuiltinBug(this, "Called C++ object pointer is null"));
        emitBadCall(BT_cxx_call_null.get(), C, CC->getCXXThisExpr());
        return;
      }
  
      State = StNonNull;
    }
  
    const Decl *D = Call.getDecl();
    if (D && (isa<FunctionDecl>(D) || isa<BlockDecl>(D))) {
      // If we have a function or block declaration, we can make sure we pass
      // enough parameters.
      unsigned Params = Call.parameters().size();
      if (Call.getNumArgs() < Params) {
        ExplodedNode *N = C.generateErrorNode();
        if (!N)
          return;
  
        LazyInit_BT("Function call with too few arguments", BT_call_few_args);
  
        SmallString<512> Str;
        llvm::raw_svector_ostream os(Str);
        if (isa<FunctionDecl>(D)) {
          os << "Function ";
        } else {
          assert(isa<BlockDecl>(D));
          os << "Block ";
        }
        os << "taking " << Params << " argument"
           << (Params == 1 ? "" : "s") << " is called with fewer ("
           << Call.getNumArgs() << ")";
  
        C.emitReport(std::make_unique<PathSensitiveBugReport>(*BT_call_few_args,
                                                              os.str(), N));
      }
    }
  
    // Don't check for uninitialized field values in arguments if the
    // caller has a body that is available and we have the chance to inline it.
    // This is a hack, but is a reasonable compromise betweens sometimes warning
    // and sometimes not depending on if we decide to inline a function.
    const bool checkUninitFields =
      !(C.getAnalysisManager().shouldInlineCall() && (D && D->getBody()));
  
    std::unique_ptr<BugType> *BT;
    if (isa<ObjCMethodCall>(Call))
      BT = &BT_msg_arg;
    else
      BT = &BT_call_arg;
  
    const FunctionDecl *FD = dyn_cast_or_null<FunctionDecl>(D);
    for (unsigned i = 0, e = Call.getNumArgs(); i != e; ++i) {
      const ParmVarDecl *ParamDecl = nullptr;
      if(FD && i < FD->getNumParams())
        ParamDecl = FD->getParamDecl(i);
      if (PreVisitProcessArg(C, Call.getArgSVal(i), Call.getArgSourceRange(i),
                             Call.getArgExpr(i), i,
                             checkUninitFields, Call, *BT, ParamDecl))
        return;
    }
  
    // If we make it here, record our assumptions about the callee.
    C.addTransition(State);
  }
  
  void CallAndMessageChecker::checkPreObjCMessage(const ObjCMethodCall &msg,
                                                  CheckerContext &C) const {
    SVal recVal = msg.getReceiverSVal();
    if (recVal.isUndef()) {
      if (ExplodedNode *N = C.generateErrorNode()) {
        BugType *BT = nullptr;
        switch (msg.getMessageKind()) {
        case OCM_Message:
          if (!BT_msg_undef)
            BT_msg_undef.reset(new BuiltinBug(this,
                                              "Receiver in message expression "
                                              "is an uninitialized value"));
          BT = BT_msg_undef.get();
          break;
        case OCM_PropertyAccess:
          if (!BT_objc_prop_undef)
            BT_objc_prop_undef.reset(new BuiltinBug(
                this, "Property access on an uninitialized object pointer"));
          BT = BT_objc_prop_undef.get();
          break;
        case OCM_Subscript:
          if (!BT_objc_subscript_undef)
            BT_objc_subscript_undef.reset(new BuiltinBug(
                this, "Subscript access on an uninitialized object pointer"));
          BT = BT_objc_subscript_undef.get();
          break;
        }
        assert(BT && "Unknown message kind.");
  
        auto R = std::make_unique<PathSensitiveBugReport>(*BT, BT->getDescription(), N);
        const ObjCMessageExpr *ME = msg.getOriginExpr();
        R->addRange(ME->getReceiverRange());
  
        // FIXME: getTrackNullOrUndefValueVisitor can't handle "super" yet.
        if (const Expr *ReceiverE = ME->getInstanceReceiver())
          bugreporter::trackExpressionValue(N, ReceiverE, *R);
        C.emitReport(std::move(R));
      }
      return;
    }
  }
  
  void CallAndMessageChecker::checkObjCMessageNil(const ObjCMethodCall &msg,
                                                  CheckerContext &C) const {
    HandleNilReceiver(C, C.getState(), msg);
  }
  
  void CallAndMessageChecker::emitNilReceiverBug(CheckerContext &C,
                                                 const ObjCMethodCall &msg,
                                                 ExplodedNode *N) const {
  
    if (!BT_msg_ret)
      BT_msg_ret.reset(
          new BuiltinBug(this, "Receiver in message expression is 'nil'"));
  
    const ObjCMessageExpr *ME = msg.getOriginExpr();
  
    QualType ResTy = msg.getResultType();
  
    SmallString<200> buf;
    llvm::raw_svector_ostream os(buf);
    os << "The receiver of message '";
    ME->getSelector().print(os);
    os << "' is nil";
    if (ResTy->isReferenceType()) {
      os << ", which results in forming a null reference";
    } else {
      os << " and returns a value of type '";
      msg.getResultType().print(os, C.getLangOpts());
      os << "' that will be garbage";
    }
  
    auto report =
        std::make_unique<PathSensitiveBugReport>(*BT_msg_ret, os.str(), N);
    report->addRange(ME->getReceiverRange());
    // FIXME: This won't track "self" in messages to super.
    if (const Expr *receiver = ME->getInstanceReceiver()) {
      bugreporter::trackExpressionValue(N, receiver, *report);
    }
    C.emitReport(std::move(report));
  }
  
  static bool supportsNilWithFloatRet(const llvm::Triple &triple) {
    return (triple.getVendor() == llvm::Triple::Apple &&
            (triple.isiOS() || triple.isWatchOS() ||
             !triple.isMacOSXVersionLT(10,5)));
  }
  
  void CallAndMessageChecker::HandleNilReceiver(CheckerContext &C,
                                                ProgramStateRef state,
                                                const ObjCMethodCall &Msg) const {
    ASTContext &Ctx = C.getASTContext();
    static CheckerProgramPointTag Tag(this, "NilReceiver");
  
    // Check the return type of the message expression.  A message to nil will
    // return different values depending on the return type and the architecture.
    QualType RetTy = Msg.getResultType();
    CanQualType CanRetTy = Ctx.getCanonicalType(RetTy);
    const LocationContext *LCtx = C.getLocationContext();
  
    if (CanRetTy->isStructureOrClassType()) {
      // Structure returns are safe since the compiler zeroes them out.
      SVal V = C.getSValBuilder().makeZeroVal(RetTy);
      C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
      return;
    }
  
    // Other cases: check if sizeof(return type) > sizeof(void*)
    if (CanRetTy != Ctx.VoidTy && C.getLocationContext()->getParentMap()
                                    .isConsumedExpr(Msg.getOriginExpr())) {
      // Compute: sizeof(void *) and sizeof(return type)
      const uint64_t voidPtrSize = Ctx.getTypeSize(Ctx.VoidPtrTy);
      const uint64_t returnTypeSize = Ctx.getTypeSize(CanRetTy);
  
      if (CanRetTy.getTypePtr()->isReferenceType()||
          (voidPtrSize < returnTypeSize &&
           !(supportsNilWithFloatRet(Ctx.getTargetInfo().getTriple()) &&
             (Ctx.FloatTy == CanRetTy ||
              Ctx.DoubleTy == CanRetTy ||
              Ctx.LongDoubleTy == CanRetTy ||
              Ctx.LongLongTy == CanRetTy ||
              Ctx.UnsignedLongLongTy == CanRetTy)))) {
        if (ExplodedNode *N = C.generateErrorNode(state, &Tag))
          emitNilReceiverBug(C, Msg, N);
        return;
      }
  
      // Handle the safe cases where the return value is 0 if the
      // receiver is nil.
      //
      // FIXME: For now take the conservative approach that we only
      // return null values if we *know* that the receiver is nil.
      // This is because we can have surprises like:
      //
      //   ... = [[NSScreens screens] objectAtIndex:0];
      //
      // What can happen is that [... screens] could return nil, but
      // it most likely isn't nil.  We should assume the semantics
      // of this case unless we have *a lot* more knowledge.
      //
      SVal V = C.getSValBuilder().makeZeroVal(RetTy);
      C.addTransition(state->BindExpr(Msg.getOriginExpr(), LCtx, V), &Tag);
      return;
    }
  
    C.addTransition(state);
  }
  
  void ento::registerCallAndMessageChecker(CheckerManager &mgr) {
    mgr.registerChecker<CallAndMessageChecker>();
  }
  
  bool ento::shouldRegisterCallAndMessageChecker(const CheckerManager &mgr) {
    return true;
  }
  
  void ento::registerCallAndMessageUnInitRefArg(CheckerManager &mgr) {
    CallAndMessageChecker *Checker = mgr.getChecker<CallAndMessageChecker>();
    Checker->Check_CallAndMessageUnInitRefArg = true;
    Checker->CheckName_CallAndMessageUnInitRefArg = mgr.getCurrentCheckerName();
  }
  
  bool ento::shouldRegisterCallAndMessageUnInitRefArg(const CheckerManager &mgr) {
    return true;
  }
  