text: //===--- FrontendAction.cpp -----------------------------------------------===//
  //
  // 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
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Frontend/FrontendAction.h"
  #include "clang/AST/ASTConsumer.h"
  #include "clang/AST/ASTContext.h"
  #include "clang/AST/DeclGroup.h"
  #include "clang/Basic/Builtins.h"
  #include "clang/Basic/LangStandard.h"
  #include "clang/Frontend/ASTUnit.h"
  #include "clang/Frontend/CompilerInstance.h"
  #include "clang/Frontend/FrontendDiagnostic.h"
  #include "clang/Frontend/FrontendPluginRegistry.h"
  #include "clang/Frontend/LayoutOverrideSource.h"
  #include "clang/Frontend/MultiplexConsumer.h"
  #include "clang/Frontend/Utils.h"
  #include "clang/Lex/HeaderSearch.h"
  #include "clang/Lex/LiteralSupport.h"
  #include "clang/Lex/Preprocessor.h"
  #include "clang/Lex/PreprocessorOptions.h"
  #include "clang/Parse/ParseAST.h"
  #include "clang/Serialization/ASTDeserializationListener.h"
  #include "clang/Serialization/ASTReader.h"
  #include "clang/Serialization/GlobalModuleIndex.h"
  #include "llvm/Support/BuryPointer.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/FileSystem.h"
  #include "llvm/Support/Path.h"
  #include "llvm/Support/Timer.h"
  #include "llvm/Support/raw_ostream.h"
  #include <system_error>
  using namespace clang;
  
  LLVM_INSTANTIATE_REGISTRY(FrontendPluginRegistry)
  
  namespace {
  
  class DelegatingDeserializationListener : public ASTDeserializationListener {
    ASTDeserializationListener *Previous;
    bool DeletePrevious;
  
  public:
    explicit DelegatingDeserializationListener(
        ASTDeserializationListener *Previous, bool DeletePrevious)
        : Previous(Previous), DeletePrevious(DeletePrevious) {}
    ~DelegatingDeserializationListener() override {
      if (DeletePrevious)
        delete Previous;
    }
  
    void ReaderInitialized(ASTReader *Reader) override {
      if (Previous)
        Previous->ReaderInitialized(Reader);
    }
    void IdentifierRead(serialization::IdentID ID,
                        IdentifierInfo *II) override {
      if (Previous)
        Previous->IdentifierRead(ID, II);
    }
    void TypeRead(serialization::TypeIdx Idx, QualType T) override {
      if (Previous)
        Previous->TypeRead(Idx, T);
    }
    void DeclRead(serialization::DeclID ID, const Decl *D) override {
      if (Previous)
        Previous->DeclRead(ID, D);
    }
    void SelectorRead(serialization::SelectorID ID, Selector Sel) override {
      if (Previous)
        Previous->SelectorRead(ID, Sel);
    }
    void MacroDefinitionRead(serialization::PreprocessedEntityID PPID,
                             MacroDefinitionRecord *MD) override {
      if (Previous)
        Previous->MacroDefinitionRead(PPID, MD);
    }
  };
  
  /// Dumps deserialized declarations.
  class DeserializedDeclsDumper : public DelegatingDeserializationListener {
  public:
    explicit DeserializedDeclsDumper(ASTDeserializationListener *Previous,
                                     bool DeletePrevious)
        : DelegatingDeserializationListener(Previous, DeletePrevious) {}
  
    void DeclRead(serialization::DeclID ID, const Decl *D) override {
      llvm::outs() << "PCH DECL: " << D->getDeclKindName();
      if (const NamedDecl *ND = dyn_cast<NamedDecl>(D)) {
        llvm::outs() << " - ";
        ND->printQualifiedName(llvm::outs());
      }
      llvm::outs() << "\n";
  
      DelegatingDeserializationListener::DeclRead(ID, D);
    }
  };
  
  /// Checks deserialized declarations and emits error if a name
  /// matches one given in command-line using -error-on-deserialized-decl.
  class DeserializedDeclsChecker : public DelegatingDeserializationListener {
    ASTContext &Ctx;
    std::set<std::string> NamesToCheck;
  
  public:
    DeserializedDeclsChecker(ASTContext &Ctx,
                             const std::set<std::string> &NamesToCheck,
                             ASTDeserializationListener *Previous,
                             bool DeletePrevious)
        : DelegatingDeserializationListener(Previous, DeletePrevious), Ctx(Ctx),
          NamesToCheck(NamesToCheck) {}
  
    void DeclRead(serialization::DeclID ID, const Decl *D) override {
      if (const NamedDecl *ND = dyn_cast<NamedDecl>(D))
        if (NamesToCheck.find(ND->getNameAsString()) != NamesToCheck.end()) {
          unsigned DiagID
            = Ctx.getDiagnostics().getCustomDiagID(DiagnosticsEngine::Error,
                                                   "%0 was deserialized");
          Ctx.getDiagnostics().Report(Ctx.getFullLoc(D->getLocation()), DiagID)
              << ND->getNameAsString();
        }
  
      DelegatingDeserializationListener::DeclRead(ID, D);
    }
  };
  
  } // end anonymous namespace
  
  FrontendAction::FrontendAction() : Instance(nullptr) {}
  
  FrontendAction::~FrontendAction() {}
  
  void FrontendAction::setCurrentInput(const FrontendInputFile &CurrentInput,
                                       std::unique_ptr<ASTUnit> AST) {
    this->CurrentInput = CurrentInput;
    CurrentASTUnit = std::move(AST);
  }
  
  Module *FrontendAction::getCurrentModule() const {
    CompilerInstance &CI = getCompilerInstance();
    return CI.getPreprocessor().getHeaderSearchInfo().lookupModule(
        CI.getLangOpts().CurrentModule, /*AllowSearch*/false);
  }
  
  std::unique_ptr<ASTConsumer>
  FrontendAction::CreateWrappedASTConsumer(CompilerInstance &CI,
                                           StringRef InFile) {
    std::unique_ptr<ASTConsumer> Consumer = CreateASTConsumer(CI, InFile);
    if (!Consumer)
      return nullptr;
  
    // Validate -add-plugin args.
    bool FoundAllPlugins = true;
    for (const std::string &Arg : CI.getFrontendOpts().AddPluginActions) {
      bool Found = false;
      for (FrontendPluginRegistry::iterator it = FrontendPluginRegistry::begin(),
                                            ie = FrontendPluginRegistry::end();
           it != ie; ++it) {
        if (it->getName() == Arg)
          Found = true;
      }
      if (!Found) {
        CI.getDiagnostics().Report(diag::err_fe_invalid_plugin_name) << Arg;
        FoundAllPlugins = false;
      }
    }
    if (!FoundAllPlugins)
      return nullptr;
  
    // If there are no registered plugins we don't need to wrap the consumer
    if (FrontendPluginRegistry::begin() == FrontendPluginRegistry::end())
      return Consumer;
  
    // If this is a code completion run, avoid invoking the plugin consumers
    if (CI.hasCodeCompletionConsumer())
      return Consumer;
  
    // Collect the list of plugins that go before the main action (in Consumers)
    // or after it (in AfterConsumers)
    std::vector<std::unique_ptr<ASTConsumer>> Consumers;
    std::vector<std::unique_ptr<ASTConsumer>> AfterConsumers;
    for (FrontendPluginRegistry::iterator it = FrontendPluginRegistry::begin(),
                                          ie = FrontendPluginRegistry::end();
         it != ie; ++it) {
      std::unique_ptr<PluginASTAction> P = it->instantiate();
      PluginASTAction::ActionType ActionType = P->getActionType();
      if (ActionType == PluginASTAction::Cmdline) {
        // This is O(|plugins| * |add_plugins|), but since both numbers are
        // way below 50 in practice, that's ok.
        for (size_t i = 0, e = CI.getFrontendOpts().AddPluginActions.size();
             i != e; ++i) {
          if (it->getName() == CI.getFrontendOpts().AddPluginActions[i]) {
            ActionType = PluginASTAction::AddAfterMainAction;
            break;
          }
        }
      }
      if ((ActionType == PluginASTAction::AddBeforeMainAction ||
           ActionType == PluginASTAction::AddAfterMainAction) &&
          P->ParseArgs(CI, CI.getFrontendOpts().PluginArgs[it->getName()])) {
        std::unique_ptr<ASTConsumer> PluginConsumer = P->CreateASTConsumer(CI, InFile);
        if (ActionType == PluginASTAction::AddBeforeMainAction) {
          Consumers.push_back(std::move(PluginConsumer));
        } else {
          AfterConsumers.push_back(std::move(PluginConsumer));
        }
      }
    }
  
    // Add to Consumers the main consumer, then all the plugins that go after it
    Consumers.push_back(std::move(Consumer));
    for (auto &C : AfterConsumers) {
      Consumers.push_back(std::move(C));
    }
  
    return std::make_unique<MultiplexConsumer>(std::move(Consumers));
  }
  
  /// For preprocessed files, if the first line is the linemarker and specifies
  /// the original source file name, use that name as the input file name.
  /// Returns the location of the first token after the line marker directive.
  ///
  /// \param CI The compiler instance.
  /// \param InputFile Populated with the filename from the line marker.
  /// \param IsModuleMap If \c true, add a line note corresponding to this line
  ///        directive. (We need to do this because the directive will not be
  ///        visited by the preprocessor.)
  static SourceLocation ReadOriginalFileName(CompilerInstance &CI,
                                             std::string &InputFile,
                                             bool IsModuleMap = false) {
    auto &SourceMgr = CI.getSourceManager();
    auto MainFileID = SourceMgr.getMainFileID();
  
    bool Invalid = false;
    const auto *MainFileBuf = SourceMgr.getBuffer(MainFileID, &Invalid);
    if (Invalid)
      return SourceLocation();
  
    std::unique_ptr<Lexer> RawLexer(
        new Lexer(MainFileID, MainFileBuf, SourceMgr, CI.getLangOpts()));
  
    // If the first line has the syntax of
    //
    // # NUM "FILENAME"
    //
    // we use FILENAME as the input file name.
    Token T;
    if (RawLexer->LexFromRawLexer(T) || T.getKind() != tok::hash)
      return SourceLocation();
    if (RawLexer->LexFromRawLexer(T) || T.isAtStartOfLine() ||
        T.getKind() != tok::numeric_constant)
      return SourceLocation();
  
    unsigned LineNo;
    SourceLocation LineNoLoc = T.getLocation();
    if (IsModuleMap) {
      llvm::SmallString<16> Buffer;
      if (Lexer::getSpelling(LineNoLoc, Buffer, SourceMgr, CI.getLangOpts())
              .getAsInteger(10, LineNo))
        return SourceLocation();
    }
  
    RawLexer->LexFromRawLexer(T);
    if (T.isAtStartOfLine() || T.getKind() != tok::string_literal)
      return SourceLocation();
  
    StringLiteralParser Literal(T, CI.getPreprocessor());
    if (Literal.hadError)
      return SourceLocation();
    RawLexer->LexFromRawLexer(T);
    if (T.isNot(tok::eof) && !T.isAtStartOfLine())
      return SourceLocation();
    InputFile = Literal.GetString().str();
  
    if (IsModuleMap)
      CI.getSourceManager().AddLineNote(
          LineNoLoc, LineNo, SourceMgr.getLineTableFilenameID(InputFile), false,
          false, SrcMgr::C_User_ModuleMap);
  
    return T.getLocation();
  }
  
  static SmallVectorImpl<char> &
  operator+=(SmallVectorImpl<char> &Includes, StringRef RHS) {
    Includes.append(RHS.begin(), RHS.end());
    return Includes;
  }
  
  static void addHeaderInclude(StringRef HeaderName,
                               SmallVectorImpl<char> &Includes,
                               const LangOptions &LangOpts,
                               bool IsExternC) {
    if (IsExternC && LangOpts.CPlusPlus)
      Includes += "extern \"C\" {\n";
    if (LangOpts.ObjC)
      Includes += "#import \"";
    else
      Includes += "#include \"";
  
    Includes += HeaderName;
  
    Includes += "\"\n";
    if (IsExternC && LangOpts.CPlusPlus)
      Includes += "}\n";
  }
  
  /// Collect the set of header includes needed to construct the given
  /// module and update the TopHeaders file set of the module.
  ///
  /// \param Module The module we're collecting includes from.
  ///
  /// \param Includes Will be augmented with the set of \#includes or \#imports
  /// needed to load all of the named headers.
  static std::error_code collectModuleHeaderIncludes(
      const LangOptions &LangOpts, FileManager &FileMgr, DiagnosticsEngine &Diag,
      ModuleMap &ModMap, clang::Module *Module, SmallVectorImpl<char> &Includes) {
    // Don't collect any headers for unavailable modules.
    if (!Module->isAvailable())
      return std::error_code();
  
    // Resolve all lazy header directives to header files.
    ModMap.resolveHeaderDirectives(Module);
  
    // If any headers are missing, we can't build this module. In most cases,
    // diagnostics for this should have already been produced; we only get here
    // if explicit stat information was provided.
    // FIXME: If the name resolves to a file with different stat information,
    // produce a better diagnostic.
    if (!Module->MissingHeaders.empty()) {
      auto &MissingHeader = Module->MissingHeaders.front();
      Diag.Report(MissingHeader.FileNameLoc, diag::err_module_header_missing)
        << MissingHeader.IsUmbrella << MissingHeader.FileName;
      return std::error_code();
    }
  
    // Add includes for each of these headers.
    for (auto HK : {Module::HK_Normal, Module::HK_Private}) {
      for (Module::Header &H : Module->Headers[HK]) {
        Module->addTopHeader(H.Entry);
        // Use the path as specified in the module map file. We'll look for this
        // file relative to the module build directory (the directory containing
        // the module map file) so this will find the same file that we found
        // while parsing the module map.
        addHeaderInclude(H.NameAsWritten, Includes, LangOpts, Module->IsExternC);
      }
    }
    // Note that Module->PrivateHeaders will not be a TopHeader.
  
    if (Module::Header UmbrellaHeader = Module->getUmbrellaHeader()) {
      Module->addTopHeader(UmbrellaHeader.Entry);
      if (Module->Parent)
        // Include the umbrella header for submodules.
        addHeaderInclude(UmbrellaHeader.NameAsWritten, Includes, LangOpts,
                         Module->IsExternC);
    } else if (Module::DirectoryName UmbrellaDir = Module->getUmbrellaDir()) {
      // Add all of the headers we find in this subdirectory.
      std::error_code EC;
      SmallString<128> DirNative;
      llvm::sys::path::native(UmbrellaDir.Entry->getName(), DirNative);
  
      llvm::vfs::FileSystem &FS = FileMgr.getVirtualFileSystem();
      for (llvm::vfs::recursive_directory_iterator Dir(FS, DirNative, EC), End;
           Dir != End && !EC; Dir.increment(EC)) {
        // Check whether this entry has an extension typically associated with
        // headers.
        if (!llvm::StringSwitch<bool>(llvm::sys::path::extension(Dir->path()))
                 .Cases(".h", ".H", ".hh", ".hpp", true)
                 .Default(false))
          continue;
  
        auto Header = FileMgr.getFile(Dir->path());
        // FIXME: This shouldn't happen unless there is a file system race. Is
        // that worth diagnosing?
        if (!Header)
          continue;
  
        // If this header is marked 'unavailable' in this module, don't include
        // it.
        if (ModMap.isHeaderUnavailableInModule(*Header, Module))
          continue;
  
        // Compute the relative path from the directory to this file.
        SmallVector<StringRef, 16> Components;
        auto PathIt = llvm::sys::path::rbegin(Dir->path());
        for (int I = 0; I != Dir.level() + 1; ++I, ++PathIt)
          Components.push_back(*PathIt);
        SmallString<128> RelativeHeader(UmbrellaDir.NameAsWritten);
        for (auto It = Components.rbegin(), End = Components.rend(); It != End;
             ++It)
          llvm::sys::path::append(RelativeHeader, *It);
  
        // Include this header as part of the umbrella directory.
        Module->addTopHeader(*Header);
        addHeaderInclude(RelativeHeader, Includes, LangOpts, Module->IsExternC);
      }
  
      if (EC)
        return EC;
    }
  
    // Recurse into submodules.
    for (clang::Module::submodule_iterator Sub = Module->submodule_begin(),
                                        SubEnd = Module->submodule_end();
         Sub != SubEnd; ++Sub)
      if (std::error_code Err = collectModuleHeaderIncludes(
              LangOpts, FileMgr, Diag, ModMap, *Sub, Includes))
        return Err;
  
    return std::error_code();
  }
  
  static bool loadModuleMapForModuleBuild(CompilerInstance &CI, bool IsSystem,
                                          bool IsPreprocessed,
                                          std::string &PresumedModuleMapFile,
                                          unsigned &Offset) {
    auto &SrcMgr = CI.getSourceManager();
    HeaderSearch &HS = CI.getPreprocessor().getHeaderSearchInfo();
  
    // Map the current input to a file.
    FileID ModuleMapID = SrcMgr.getMainFileID();
    const FileEntry *ModuleMap = SrcMgr.getFileEntryForID(ModuleMapID);
  
    // If the module map is preprocessed, handle the initial line marker;
    // line directives are not part of the module map syntax in general.
    Offset = 0;
    if (IsPreprocessed) {
      SourceLocation EndOfLineMarker =
          ReadOriginalFileName(CI, PresumedModuleMapFile, /*IsModuleMap*/ true);
      if (EndOfLineMarker.isValid())
        Offset = CI.getSourceManager().getDecomposedLoc(EndOfLineMarker).second;
    }
  
    // Load the module map file.
    if (HS.loadModuleMapFile(ModuleMap, IsSystem, ModuleMapID, &Offset,
                             PresumedModuleMapFile))
      return true;
  
    if (SrcMgr.getBuffer(ModuleMapID)->getBufferSize() == Offset)
      Offset = 0;
  
    return false;
  }
  
  static Module *prepareToBuildModule(CompilerInstance &CI,
                                      StringRef ModuleMapFilename) {
    if (CI.getLangOpts().CurrentModule.empty()) {
      CI.getDiagnostics().Report(diag::err_missing_module_name);
  
      // FIXME: Eventually, we could consider asking whether there was just
      // a single module described in the module map, and use that as a
      // default. Then it would be fairly trivial to just "compile" a module
      // map with a single module (the common case).
      return nullptr;
    }
  
    // Dig out the module definition.
    HeaderSearch &HS = CI.getPreprocessor().getHeaderSearchInfo();
    Module *M = HS.lookupModule(CI.getLangOpts().CurrentModule,
                                /*AllowSearch=*/false);
    if (!M) {
      CI.getDiagnostics().Report(diag::err_missing_module)
        << CI.getLangOpts().CurrentModule << ModuleMapFilename;
  
      return nullptr;
    }
  
    // Check whether we can build this module at all.
    if (Preprocessor::checkModuleIsAvailable(CI.getLangOpts(), CI.getTarget(),
                                             CI.getDiagnostics(), M))
      return nullptr;
  
    // Inform the preprocessor that includes from within the input buffer should
    // be resolved relative to the build directory of the module map file.
    CI.getPreprocessor().setMainFileDir(M->Directory);
  
    // If the module was inferred from a different module map (via an expanded
    // umbrella module definition), track that fact.
    // FIXME: It would be preferable to fill this in as part of processing
    // the module map, rather than adding it after the fact.
    StringRef OriginalModuleMapName = CI.getFrontendOpts().OriginalModuleMap;
    if (!OriginalModuleMapName.empty()) {
      auto OriginalModuleMap =
          CI.getFileManager().getFile(OriginalModuleMapName,
                                      /*openFile*/ true);
      if (!OriginalModuleMap) {
        CI.getDiagnostics().Report(diag::err_module_map_not_found)
          << OriginalModuleMapName;
        return nullptr;
      }
      if (*OriginalModuleMap != CI.getSourceManager().getFileEntryForID(
                                   CI.getSourceManager().getMainFileID())) {
        M->IsInferred = true;
        CI.getPreprocessor().getHeaderSearchInfo().getModuleMap()
          .setInferredModuleAllowedBy(M, *OriginalModuleMap);
      }
    }
  
    // If we're being run from the command-line, the module build stack will not
    // have been filled in yet, so complete it now in order to allow us to detect
    // module cycles.
    SourceManager &SourceMgr = CI.getSourceManager();
    if (SourceMgr.getModuleBuildStack().empty())
      SourceMgr.pushModuleBuildStack(CI.getLangOpts().CurrentModule,
                                     FullSourceLoc(SourceLocation(), SourceMgr));
    return M;
  }
  
  /// Compute the input buffer that should be used to build the specified module.
  static std::unique_ptr<llvm::MemoryBuffer>
  getInputBufferForModule(CompilerInstance &CI, Module *M) {
    FileManager &FileMgr = CI.getFileManager();
  
    // Collect the set of #includes we need to build the module.
    SmallString<256> HeaderContents;
    std::error_code Err = std::error_code();
    if (Module::Header UmbrellaHeader = M->getUmbrellaHeader())
      addHeaderInclude(UmbrellaHeader.NameAsWritten, HeaderContents,
                       CI.getLangOpts(), M->IsExternC);
    Err = collectModuleHeaderIncludes(
        CI.getLangOpts(), FileMgr, CI.getDiagnostics(),
        CI.getPreprocessor().getHeaderSearchInfo().getModuleMap(), M,
        HeaderContents);
  
    if (Err) {
      CI.getDiagnostics().Report(diag::err_module_cannot_create_includes)
        << M->getFullModuleName() << Err.message();
      return nullptr;
    }
  
    return llvm::MemoryBuffer::getMemBufferCopy(
        HeaderContents, Module::getModuleInputBufferName());
  }
  
  bool FrontendAction::BeginSourceFile(CompilerInstance &CI,
                                       const FrontendInputFile &RealInput) {
    FrontendInputFile Input(RealInput);
    assert(!Instance && "Already processing a source file!");
    assert(!Input.isEmpty() && "Unexpected empty filename!");
    setCurrentInput(Input);
    setCompilerInstance(&CI);
  
    bool HasBegunSourceFile = false;
    bool ReplayASTFile = Input.getKind().getFormat() == InputKind::Precompiled &&
                         usesPreprocessorOnly();
    if (!BeginInvocation(CI))
      goto failure;
  
    // If we're replaying the build of an AST file, import it and set up
    // the initial state from its build.
    if (ReplayASTFile) {
      IntrusiveRefCntPtr<DiagnosticsEngine> Diags(&CI.getDiagnostics());
  
      // The AST unit populates its own diagnostics engine rather than ours.
      IntrusiveRefCntPtr<DiagnosticsEngine> ASTDiags(
          new DiagnosticsEngine(Diags->getDiagnosticIDs(),
                                &Diags->getDiagnosticOptions()));
      ASTDiags->setClient(Diags->getClient(), /*OwnsClient*/false);
  
      // FIXME: What if the input is a memory buffer?
      StringRef InputFile = Input.getFile();
  
      std::unique_ptr<ASTUnit> AST = ASTUnit::LoadFromASTFile(
          InputFile, CI.getPCHContainerReader(), ASTUnit::LoadPreprocessorOnly,
          ASTDiags, CI.getFileSystemOpts(), CI.getCodeGenOpts().DebugTypeExtRefs);
      if (!AST)
        goto failure;
  
      // Options relating to how we treat the input (but not what we do with it)
      // are inherited from the AST unit.
      CI.getHeaderSearchOpts() = AST->getHeaderSearchOpts();
      CI.getPreprocessorOpts() = AST->getPreprocessorOpts();
      CI.getLangOpts() = AST->getLangOpts();
  
      // Set the shared objects, these are reset when we finish processing the
      // file, otherwise the CompilerInstance will happily destroy them.
      CI.setFileManager(&AST->getFileManager());
      CI.createSourceManager(CI.getFileManager());
      CI.getSourceManager().initializeForReplay(AST->getSourceManager());
  
      // Preload all the module files loaded transitively by the AST unit. Also
      // load all module map files that were parsed as part of building the AST
      // unit.
      if (auto ASTReader = AST->getASTReader()) {
        auto &MM = ASTReader->getModuleManager();
        auto &PrimaryModule = MM.getPrimaryModule();
  
        for (serialization::ModuleFile &MF : MM)
          if (&MF != &PrimaryModule)
            CI.getFrontendOpts().ModuleFiles.push_back(MF.FileName);
  
        ASTReader->visitTopLevelModuleMaps(PrimaryModule,
                                           [&](const FileEntry *FE) {
          CI.getFrontendOpts().ModuleMapFiles.push_back(FE->getName());
        });
      }
  
      // Set up the input file for replay purposes.
      auto Kind = AST->getInputKind();
      if (Kind.getFormat() == InputKind::ModuleMap) {
        Module *ASTModule =
            AST->getPreprocessor().getHeaderSearchInfo().lookupModule(
                AST->getLangOpts().CurrentModule, /*AllowSearch*/ false);
        assert(ASTModule && "module file does not define its own module");
        Input = FrontendInputFile(ASTModule->PresumedModuleMapFile, Kind);
      } else {
        auto &OldSM = AST->getSourceManager();
        FileID ID = OldSM.getMainFileID();
        if (auto *File = OldSM.getFileEntryForID(ID))
          Input = FrontendInputFile(File->getName(), Kind);
        else
          Input = FrontendInputFile(OldSM.getBuffer(ID), Kind);
      }
      setCurrentInput(Input, std::move(AST));
    }
  
    // AST files follow a very different path, since they share objects via the
    // AST unit.
    if (Input.getKind().getFormat() == InputKind::Precompiled) {
      assert(!usesPreprocessorOnly() && "this case was handled above");
      assert(hasASTFileSupport() &&
             "This action does not have AST file support!");
  
      IntrusiveRefCntPtr<DiagnosticsEngine> Diags(&CI.getDiagnostics());
  
      // FIXME: What if the input is a memory buffer?
      StringRef InputFile = Input.getFile();
  
      std::unique_ptr<ASTUnit> AST = ASTUnit::LoadFromASTFile(
          InputFile, CI.getPCHContainerReader(), ASTUnit::LoadEverything, Diags,
          CI.getFileSystemOpts(), CI.getCodeGenOpts().DebugTypeExtRefs);
  
      if (!AST)
        goto failure;
  
      // Inform the diagnostic client we are processing a source file.
      CI.getDiagnosticClient().BeginSourceFile(CI.getLangOpts(), nullptr);
      HasBegunSourceFile = true;
  
      // Set the shared objects, these are reset when we finish processing the
      // file, otherwise the CompilerInstance will happily destroy them.
      CI.setFileManager(&AST->getFileManager());
      CI.setSourceManager(&AST->getSourceManager());
      CI.setPreprocessor(AST->getPreprocessorPtr());
      Preprocessor &PP = CI.getPreprocessor();
      PP.getBuiltinInfo().initializeBuiltins(PP.getIdentifierTable(),
                                             PP.getLangOpts());
      CI.setASTContext(&AST->getASTContext());
  
      setCurrentInput(Input, std::move(AST));
  
      // Initialize the action.
      if (!BeginSourceFileAction(CI))
        goto failure;
  
      // Create the AST consumer.
      CI.setASTConsumer(CreateWrappedASTConsumer(CI, InputFile));
      if (!CI.hasASTConsumer())
        goto failure;
  
      return true;
    }
  
    // Set up the file and source managers, if needed.
    if (!CI.hasFileManager()) {
      if (!CI.createFileManager()) {
        goto failure;
      }
    }
    if (!CI.hasSourceManager())
      CI.createSourceManager(CI.getFileManager());
  
    // Set up embedding for any specified files. Do this before we load any
    // source files, including the primary module map for the compilation.
    for (const auto &F : CI.getFrontendOpts().ModulesEmbedFiles) {
      if (auto FE = CI.getFileManager().getFile(F, /*openFile*/true))
        CI.getSourceManager().setFileIsTransient(*FE);
      else
        CI.getDiagnostics().Report(diag::err_modules_embed_file_not_found) << F;
    }
    if (CI.getFrontendOpts().ModulesEmbedAllFiles)
      CI.getSourceManager().setAllFilesAreTransient(true);
  
    // IR files bypass the rest of initialization.
    if (Input.getKind().getLanguage() == Language::LLVM_IR) {
      assert(hasIRSupport() &&
             "This action does not have IR file support!");
  
      // Inform the diagnostic client we are processing a source file.
      CI.getDiagnosticClient().BeginSourceFile(CI.getLangOpts(), nullptr);
      HasBegunSourceFile = true;
  
      // Initialize the action.
      if (!BeginSourceFileAction(CI))
        goto failure;
  
      // Initialize the main file entry.
      if (!CI.InitializeSourceManager(CurrentInput))
        goto failure;
  
      return true;
    }
  
    // If the implicit PCH include is actually a directory, rather than
    // a single file, search for a suitable PCH file in that directory.
    if (!CI.getPreprocessorOpts().ImplicitPCHInclude.empty()) {
      FileManager &FileMgr = CI.getFileManager();
      PreprocessorOptions &PPOpts = CI.getPreprocessorOpts();
      StringRef PCHInclude = PPOpts.ImplicitPCHInclude;
      std::string SpecificModuleCachePath = CI.getSpecificModuleCachePath();
      if (auto PCHDir = FileMgr.getDirectory(PCHInclude)) {
        std::error_code EC;
        SmallString<128> DirNative;
        llvm::sys::path::native((*PCHDir)->getName(), DirNative);
        bool Found = false;
        llvm::vfs::FileSystem &FS = FileMgr.getVirtualFileSystem();
        for (llvm::vfs::directory_iterator Dir = FS.dir_begin(DirNative, EC),
                                           DirEnd;
             Dir != DirEnd && !EC; Dir.increment(EC)) {
          // Check whether this is an acceptable AST file.
          if (ASTReader::isAcceptableASTFile(
                  Dir->path(), FileMgr, CI.getPCHContainerReader(),
                  CI.getLangOpts(), CI.getTargetOpts(), CI.getPreprocessorOpts(),
                  SpecificModuleCachePath)) {
            PPOpts.ImplicitPCHInclude = Dir->path();
            Found = true;
            break;
          }
        }
  
        if (!Found) {
          CI.getDiagnostics().Report(diag::err_fe_no_pch_in_dir) << PCHInclude;
          goto failure;
        }
      }
    }
  
    // Set up the preprocessor if needed. When parsing model files the
    // preprocessor of the original source is reused.
    if (!isModelParsingAction())
      CI.createPreprocessor(getTranslationUnitKind());
  
    // Inform the diagnostic client we are processing a source file.
    CI.getDiagnosticClient().BeginSourceFile(CI.getLangOpts(),
                                             &CI.getPreprocessor());
    HasBegunSourceFile = true;
  
    // Initialize the main file entry.
    if (!CI.InitializeSourceManager(Input))
      goto failure;
  
    // For module map files, we first parse the module map and synthesize a
    // "<module-includes>" buffer before more conventional processing.
    if (Input.getKind().getFormat() == InputKind::ModuleMap) {
      CI.getLangOpts().setCompilingModule(LangOptions::CMK_ModuleMap);
  
      std::string PresumedModuleMapFile;
      unsigned OffsetToContents;
      if (loadModuleMapForModuleBuild(CI, Input.isSystem(),
                                      Input.isPreprocessed(),
                                      PresumedModuleMapFile, OffsetToContents))
        goto failure;
  
      auto *CurrentModule = prepareToBuildModule(CI, Input.getFile());
      if (!CurrentModule)
        goto failure;
  
      CurrentModule->PresumedModuleMapFile = PresumedModuleMapFile;
  
      if (OffsetToContents)
        // If the module contents are in the same file, skip to them.
        CI.getPreprocessor().setSkipMainFilePreamble(OffsetToContents, true);
      else {
        // Otherwise, convert the module description to a suitable input buffer.
        auto Buffer = getInputBufferForModule(CI, CurrentModule);
        if (!Buffer)
          goto failure;
  
        // Reinitialize the main file entry to refer to the new input.
        auto Kind = CurrentModule->IsSystem ? SrcMgr::C_System : SrcMgr::C_User;
        auto &SourceMgr = CI.getSourceManager();
        auto BufferID = SourceMgr.createFileID(std::move(Buffer), Kind);
        assert(BufferID.isValid() && "couldn't creaate module buffer ID");
        SourceMgr.setMainFileID(BufferID);
      }
    }
  
    // Initialize the action.
    if (!BeginSourceFileAction(CI))
      goto failure;
  
    // If we were asked to load any module map files, do so now.
    for (const auto &Filename : CI.getFrontendOpts().ModuleMapFiles) {
      if (auto File = CI.getFileManager().getFile(Filename))
        CI.getPreprocessor().getHeaderSearchInfo().loadModuleMapFile(
            *File, /*IsSystem*/false);
      else
        CI.getDiagnostics().Report(diag::err_module_map_not_found) << Filename;
    }
  
    // Add a module declaration scope so that modules from -fmodule-map-file
    // arguments may shadow modules found implicitly in search paths.
    CI.getPreprocessor()
        .getHeaderSearchInfo()
        .getModuleMap()
        .finishModuleDeclarationScope();
  
    // Create the AST context and consumer unless this is a preprocessor only
    // action.
    if (!usesPreprocessorOnly()) {
      // Parsing a model file should reuse the existing ASTContext.
      if (!isModelParsingAction())
        CI.createASTContext();
  
      // For preprocessed files, check if the first line specifies the original
      // source file name with a linemarker.
      std::string PresumedInputFile = getCurrentFileOrBufferName();
      if (Input.isPreprocessed())
        ReadOriginalFileName(CI, PresumedInputFile);
  
      std::unique_ptr<ASTConsumer> Consumer =
          CreateWrappedASTConsumer(CI, PresumedInputFile);
      if (!Consumer)
        goto failure;
  
      // FIXME: should not overwrite ASTMutationListener when parsing model files?
      if (!isModelParsingAction())
        CI.getASTContext().setASTMutationListener(Consumer->GetASTMutationListener());
  
      if (!CI.getPreprocessorOpts().ChainedIncludes.empty()) {
        // Convert headers to PCH and chain them.
        IntrusiveRefCntPtr<ExternalSemaSource> source, FinalReader;
        source = createChainedIncludesSource(CI, FinalReader);
        if (!source)
          goto failure;
        CI.setModuleManager(static_cast<ASTReader *>(FinalReader.get()));
        CI.getASTContext().setExternalSource(source);
      } else if (CI.getLangOpts().Modules ||
                 !CI.getPreprocessorOpts().ImplicitPCHInclude.empty()) {
        // Use PCM or PCH.
        assert(hasPCHSupport() && "This action does not have PCH support!");
        ASTDeserializationListener *DeserialListener =
            Consumer->GetASTDeserializationListener();
        bool DeleteDeserialListener = false;
        if (CI.getPreprocessorOpts().DumpDeserializedPCHDecls) {
          DeserialListener = new DeserializedDeclsDumper(DeserialListener,
                                                         DeleteDeserialListener);
          DeleteDeserialListener = true;
        }
        if (!CI.getPreprocessorOpts().DeserializedPCHDeclsToErrorOn.empty()) {
          DeserialListener = new DeserializedDeclsChecker(
              CI.getASTContext(),
              CI.getPreprocessorOpts().DeserializedPCHDeclsToErrorOn,
              DeserialListener, DeleteDeserialListener);
          DeleteDeserialListener = true;
        }
        if (!CI.getPreprocessorOpts().ImplicitPCHInclude.empty()) {
          CI.createPCHExternalASTSource(
              CI.getPreprocessorOpts().ImplicitPCHInclude,
              CI.getPreprocessorOpts().DisablePCHValidation,
            CI.getPreprocessorOpts().AllowPCHWithCompilerErrors, DeserialListener,
              DeleteDeserialListener);
          if (!CI.getASTContext().getExternalSource())
            goto failure;
        }
        // If modules are enabled, create the module manager before creating
        // any builtins, so that all declarations know that they might be
        // extended by an external source.
        if (CI.getLangOpts().Modules || !CI.hasASTContext() ||
            !CI.getASTContext().getExternalSource()) {
          CI.createASTReader();
          CI.getASTReader()->setDeserializationListener(DeserialListener,
                                                        DeleteDeserialListener);
        }
      }
  
      CI.setASTConsumer(std::move(Consumer));
      if (!CI.hasASTConsumer())
        goto failure;
    }
  
    // Initialize built-in info as long as we aren't using an external AST
    // source.
    if (CI.getLangOpts().Modules || !CI.hasASTContext() ||
        !CI.getASTContext().getExternalSource()) {
      Preprocessor &PP = CI.getPreprocessor();
      PP.getBuiltinInfo().initializeBuiltins(PP.getIdentifierTable(),
                                             PP.getLangOpts());
    } else {
      // FIXME: If this is a problem, recover from it by creating a multiplex
      // source.
      assert((!CI.getLangOpts().Modules || CI.getASTReader()) &&
             "modules enabled but created an external source that "
             "doesn't support modules");
    }
  
    // If we were asked to load any module files, do so now.
    for (const auto &ModuleFile : CI.getFrontendOpts().ModuleFiles)
      if (!CI.loadModuleFile(ModuleFile))
        goto failure;
  
    // If there is a layout overrides file, attach an external AST source that
    // provides the layouts from that file.
    if (!CI.getFrontendOpts().OverrideRecordLayoutsFile.empty() &&
        CI.hasASTContext() && !CI.getASTContext().getExternalSource()) {
      IntrusiveRefCntPtr<ExternalASTSource>
        Override(new LayoutOverrideSource(
                       CI.getFrontendOpts().OverrideRecordLayoutsFile));
      CI.getASTContext().setExternalSource(Override);
    }
  
    return true;
  
    // If we failed, reset state since the client will not end up calling the
    // matching EndSourceFile().
  failure:
    if (HasBegunSourceFile)
      CI.getDiagnosticClient().EndSourceFile();
    CI.clearOutputFiles(/*EraseFiles=*/true);
    CI.getLangOpts().setCompilingModule(LangOptions::CMK_None);
    setCurrentInput(FrontendInputFile());
    setCompilerInstance(nullptr);
    return false;
  }
  
  llvm::Error FrontendAction::Execute() {
    CompilerInstance &CI = getCompilerInstance();
  
    if (CI.hasFrontendTimer()) {
      llvm::TimeRegion Timer(CI.getFrontendTimer());
      ExecuteAction();
    }
    else ExecuteAction();
  
    // If we are supposed to rebuild the global module index, do so now unless
    // there were any module-build failures.
    if (CI.shouldBuildGlobalModuleIndex() && CI.hasFileManager() &&
        CI.hasPreprocessor()) {
      StringRef Cache =
          CI.getPreprocessor().getHeaderSearchInfo().getModuleCachePath();
      if (!Cache.empty()) {
        if (llvm::Error Err = GlobalModuleIndex::writeIndex(
                CI.getFileManager(), CI.getPCHContainerReader(), Cache)) {
          // FIXME this drops the error on the floor, but
          // Index/pch-from-libclang.c seems to rely on dropping at least some of
          // the error conditions!
          consumeError(std::move(Err));
        }
      }
    }
  
    return llvm::Error::success();
  }
  
  void FrontendAction::EndSourceFile() {
    CompilerInstance &CI = getCompilerInstance();
  
    // Inform the diagnostic client we are done with this source file.
    CI.getDiagnosticClient().EndSourceFile();
  
    // Inform the preprocessor we are done.
    if (CI.hasPreprocessor())
      CI.getPreprocessor().EndSourceFile();
  
    // Finalize the action.
    EndSourceFileAction();
  
    // Sema references the ast consumer, so reset sema first.
    //
    // FIXME: There is more per-file stuff we could just drop here?
    bool DisableFree = CI.getFrontendOpts().DisableFree;
    if (DisableFree) {
      CI.resetAndLeakSema();
      CI.resetAndLeakASTContext();
      llvm::BuryPointer(CI.takeASTConsumer().get());
    } else {
      CI.setSema(nullptr);
      CI.setASTContext(nullptr);
      CI.setASTConsumer(nullptr);
    }
  
    if (CI.getFrontendOpts().ShowStats) {
      llvm::errs() << "\nSTATISTICS FOR '" << getCurrentFile() << "':\n";
      CI.getPreprocessor().PrintStats();
      CI.getPreprocessor().getIdentifierTable().PrintStats();
      CI.getPreprocessor().getHeaderSearchInfo().PrintStats();
      CI.getSourceManager().PrintStats();
      llvm::errs() << "\n";
    }
  
    // Cleanup the output streams, and erase the output files if instructed by the
    // FrontendAction.
    CI.clearOutputFiles(/*EraseFiles=*/shouldEraseOutputFiles());
  
    if (isCurrentFileAST()) {
      if (DisableFree) {
        CI.resetAndLeakPreprocessor();
        CI.resetAndLeakSourceManager();
        CI.resetAndLeakFileManager();
        llvm::BuryPointer(std::move(CurrentASTUnit));
      } else {
        CI.setPreprocessor(nullptr);
        CI.setSourceManager(nullptr);
        CI.setFileManager(nullptr);
      }
    }
  
    setCompilerInstance(nullptr);
    setCurrentInput(FrontendInputFile());
    CI.getLangOpts().setCompilingModule(LangOptions::CMK_None);
  }
  
  bool FrontendAction::shouldEraseOutputFiles() {
    return getCompilerInstance().getDiagnostics().hasErrorOccurred();
  }
  
  //===----------------------------------------------------------------------===//
  // Utility Actions
  //===----------------------------------------------------------------------===//
  
  void ASTFrontendAction::ExecuteAction() {
    CompilerInstance &CI = getCompilerInstance();
    if (!CI.hasPreprocessor())
      return;
  
    // FIXME: Move the truncation aspect of this into Sema, we delayed this till
    // here so the source manager would be initialized.
    if (hasCodeCompletionSupport() &&
        !CI.getFrontendOpts().CodeCompletionAt.FileName.empty())
      CI.createCodeCompletionConsumer();
  
    // Use a code completion consumer?
    CodeCompleteConsumer *CompletionConsumer = nullptr;
    if (CI.hasCodeCompletionConsumer())
      CompletionConsumer = &CI.getCodeCompletionConsumer();
  
    if (!CI.hasSema())
      CI.createSema(getTranslationUnitKind(), CompletionConsumer);
  
    ParseAST(CI.getSema(), CI.getFrontendOpts().ShowStats,
             CI.getFrontendOpts().SkipFunctionBodies);
  }
  
  void PluginASTAction::anchor() { }
  
  std::unique_ptr<ASTConsumer>
  PreprocessorFrontendAction::CreateASTConsumer(CompilerInstance &CI,
                                                StringRef InFile) {
    llvm_unreachable("Invalid CreateASTConsumer on preprocessor action!");
  }
  
  bool WrapperFrontendAction::PrepareToExecuteAction(CompilerInstance &CI) {
    return WrappedAction->PrepareToExecuteAction(CI);
  }
  std::unique_ptr<ASTConsumer>
  WrapperFrontendAction::CreateASTConsumer(CompilerInstance &CI,
                                           StringRef InFile) {
    return WrappedAction->CreateASTConsumer(CI, InFile);
  }
  bool WrapperFrontendAction::BeginInvocation(CompilerInstance &CI) {
    return WrappedAction->BeginInvocation(CI);
  }
  bool WrapperFrontendAction::BeginSourceFileAction(CompilerInstance &CI) {
    WrappedAction->setCurrentInput(getCurrentInput());
    WrappedAction->setCompilerInstance(&CI);
    auto Ret = WrappedAction->BeginSourceFileAction(CI);
    // BeginSourceFileAction may change CurrentInput, e.g. during module builds.
    setCurrentInput(WrappedAction->getCurrentInput());
    return Ret;
  }
  void WrapperFrontendAction::ExecuteAction() {
    WrappedAction->ExecuteAction();
  }
  void WrapperFrontendAction::EndSourceFileAction() {
    WrappedAction->EndSourceFileAction();
  }
  
  bool WrapperFrontendAction::usesPreprocessorOnly() const {
    return WrappedAction->usesPreprocessorOnly();
  }
  TranslationUnitKind WrapperFrontendAction::getTranslationUnitKind() {
    return WrappedAction->getTranslationUnitKind();
  }
  bool WrapperFrontendAction::hasPCHSupport() const {
    return WrappedAction->hasPCHSupport();
  }
  bool WrapperFrontendAction::hasASTFileSupport() const {
    return WrappedAction->hasASTFileSupport();
  }
  bool WrapperFrontendAction::hasIRSupport() const {
    return WrappedAction->hasIRSupport();
  }
  bool WrapperFrontendAction::hasCodeCompletionSupport() const {
    return WrappedAction->hasCodeCompletionSupport();
  }
  
  WrapperFrontendAction::WrapperFrontendAction(
      std::unique_ptr<FrontendAction> WrappedAction)
    : WrappedAction(std::move(WrappedAction)) {}
  
  