text: //===--- PPLexerChange.cpp - Handle changing lexers in the preprocessor ---===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements pieces of the Preprocessor interface that manage the
  // current lexer stack.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Lex/Preprocessor.h"
  #include "clang/Basic/FileManager.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Lex/HeaderSearch.h"
  #include "clang/Lex/LexDiagnostic.h"
  #include "clang/Lex/MacroInfo.h"
  #include "clang/Lex/PTHManager.h"
  #include "llvm/ADT/StringSwitch.h"
  #include "llvm/Support/FileSystem.h"
  #include "llvm/Support/MemoryBuffer.h"
  #include "llvm/Support/Path.h"
  using namespace clang;
  
  PPCallbacks::~PPCallbacks() {}
  
  //===----------------------------------------------------------------------===//
  // Miscellaneous Methods.
  //===----------------------------------------------------------------------===//
  
  /// isInPrimaryFile - Return true if we're in the top-level file, not in a
  /// \#include.  This looks through macro expansions and active _Pragma lexers.
  bool Preprocessor::isInPrimaryFile() const {
    if (IsFileLexer())
      return IncludeMacroStack.empty();
  
    // If there are any stacked lexers, we're in a #include.
    assert(IsFileLexer(IncludeMacroStack[0]) &&
           "Top level include stack isn't our primary lexer?");
    for (unsigned i = 1, e = IncludeMacroStack.size(); i != e; ++i)
      if (IsFileLexer(IncludeMacroStack[i]))
        return false;
    return true;
  }
  
  /// getCurrentLexer - Return the current file lexer being lexed from.  Note
  /// that this ignores any potentially active macro expansions and _Pragma
  /// expansions going on at the time.
  PreprocessorLexer *Preprocessor::getCurrentFileLexer() const {
    if (IsFileLexer())
      return CurPPLexer;
  
    // Look for a stacked lexer.
    for (unsigned i = IncludeMacroStack.size(); i != 0; --i) {
      const IncludeStackInfo& ISI = IncludeMacroStack[i-1];
      if (IsFileLexer(ISI))
        return ISI.ThePPLexer;
    }
    return nullptr;
  }
  
  
  //===----------------------------------------------------------------------===//
  // Methods for Entering and Callbacks for leaving various contexts
  //===----------------------------------------------------------------------===//
  
  /// EnterSourceFile - Add a source file to the top of the include stack and
  /// start lexing tokens from it instead of the current buffer.
  bool Preprocessor::EnterSourceFile(FileID FID, const DirectoryLookup *CurDir,
                                     SourceLocation Loc) {
    assert(!CurTokenLexer && "Cannot #include a file inside a macro!");
    ++NumEnteredSourceFiles;
  
    if (MaxIncludeStackDepth < IncludeMacroStack.size())
      MaxIncludeStackDepth = IncludeMacroStack.size();
  
    if (PTH) {
      if (PTHLexer *PL = PTH->CreateLexer(FID)) {
        EnterSourceFileWithPTH(PL, CurDir);
        return false;
      }
    }
    
    // Get the MemoryBuffer for this FID, if it fails, we fail.
    bool Invalid = false;
    const llvm::MemoryBuffer *InputFile = 
      getSourceManager().getBuffer(FID, Loc, &Invalid);
    if (Invalid) {
      SourceLocation FileStart = SourceMgr.getLocForStartOfFile(FID);
      Diag(Loc, diag::err_pp_error_opening_file)
        << std::string(SourceMgr.getBufferName(FileStart)) << "";
      return true;
    }
  
    if (isCodeCompletionEnabled() &&
        SourceMgr.getFileEntryForID(FID) == CodeCompletionFile) {
      CodeCompletionFileLoc = SourceMgr.getLocForStartOfFile(FID);
      CodeCompletionLoc =
          CodeCompletionFileLoc.getLocWithOffset(CodeCompletionOffset);
    }
  
    EnterSourceFileWithLexer(new Lexer(FID, InputFile, *this), CurDir);
    return false;
  }
  
  /// EnterSourceFileWithLexer - Add a source file to the top of the include stack
  ///  and start lexing tokens from it instead of the current buffer.
  void Preprocessor::EnterSourceFileWithLexer(Lexer *TheLexer,
                                              const DirectoryLookup *CurDir) {
  
    // Add the current lexer to the include stack.
    if (CurPPLexer || CurTokenLexer)
      PushIncludeMacroStack();
  
    CurLexer.reset(TheLexer);
    CurPPLexer = TheLexer;
    CurDirLookup = CurDir;
    CurSubmodule = nullptr;
    if (CurLexerKind != CLK_LexAfterModuleImport)
      CurLexerKind = CLK_Lexer;
  
    // Notify the client, if desired, that we are in a new source file.
    if (Callbacks && !CurLexer->Is_PragmaLexer) {
      SrcMgr::CharacteristicKind FileType =
         SourceMgr.getFileCharacteristic(CurLexer->getFileLoc());
  
      Callbacks->FileChanged(CurLexer->getFileLoc(),
                             PPCallbacks::EnterFile, FileType);
    }
  }
  
  /// EnterSourceFileWithPTH - Add a source file to the top of the include stack
  /// and start getting tokens from it using the PTH cache.
  void Preprocessor::EnterSourceFileWithPTH(PTHLexer *PL,
                                            const DirectoryLookup *CurDir) {
  
    if (CurPPLexer || CurTokenLexer)
      PushIncludeMacroStack();
  
    CurDirLookup = CurDir;
    CurPTHLexer.reset(PL);
    CurPPLexer = CurPTHLexer.get();
    CurSubmodule = nullptr;
    if (CurLexerKind != CLK_LexAfterModuleImport)
      CurLexerKind = CLK_PTHLexer;
    
    // Notify the client, if desired, that we are in a new source file.
    if (Callbacks) {
      FileID FID = CurPPLexer->getFileID();
      SourceLocation EnterLoc = SourceMgr.getLocForStartOfFile(FID);
      SrcMgr::CharacteristicKind FileType =
        SourceMgr.getFileCharacteristic(EnterLoc);
      Callbacks->FileChanged(EnterLoc, PPCallbacks::EnterFile, FileType);
    }
  }
  
  /// EnterMacro - Add a Macro to the top of the include stack and start lexing
  /// tokens from it instead of the current buffer.
  void Preprocessor::EnterMacro(Token &Tok, SourceLocation ILEnd,
                                MacroInfo *Macro, MacroArgs *Args) {
    std::unique_ptr<TokenLexer> TokLexer;
    if (NumCachedTokenLexers == 0) {
      TokLexer = llvm::make_unique<TokenLexer>(Tok, ILEnd, Macro, Args, *this);
    } else {
      TokLexer = std::move(TokenLexerCache[--NumCachedTokenLexers]);
      TokLexer->Init(Tok, ILEnd, Macro, Args);
    }
  
    PushIncludeMacroStack();
    CurDirLookup = nullptr;
    CurTokenLexer = std::move(TokLexer);
    if (CurLexerKind != CLK_LexAfterModuleImport)
      CurLexerKind = CLK_TokenLexer;
  }
  
  /// EnterTokenStream - Add a "macro" context to the top of the include stack,
  /// which will cause the lexer to start returning the specified tokens.
  ///
  /// If DisableMacroExpansion is true, tokens lexed from the token stream will
  /// not be subject to further macro expansion.  Otherwise, these tokens will
  /// be re-macro-expanded when/if expansion is enabled.
  ///
  /// If OwnsTokens is false, this method assumes that the specified stream of
  /// tokens has a permanent owner somewhere, so they do not need to be copied.
  /// If it is true, it assumes the array of tokens is allocated with new[] and
  /// must be freed.
  ///
  void Preprocessor::EnterTokenStream(const Token *Toks, unsigned NumToks,
                                      bool DisableMacroExpansion,
                                      bool OwnsTokens) {
    if (CurLexerKind == CLK_CachingLexer) {
      if (CachedLexPos < CachedTokens.size()) {
        // We're entering tokens into the middle of our cached token stream. We
        // can't represent that, so just insert the tokens into the buffer.
        CachedTokens.insert(CachedTokens.begin() + CachedLexPos,
                            Toks, Toks + NumToks);
        if (OwnsTokens)
          delete [] Toks;
        return;
      }
  
      // New tokens are at the end of the cached token sequnece; insert the
      // token stream underneath the caching lexer.
      ExitCachingLexMode();
      EnterTokenStream(Toks, NumToks, DisableMacroExpansion, OwnsTokens);
      EnterCachingLexMode();
      return;
    }
  
    // Create a macro expander to expand from the specified token stream.
    std::unique_ptr<TokenLexer> TokLexer;
    if (NumCachedTokenLexers == 0) {
      TokLexer = llvm::make_unique<TokenLexer>(
          Toks, NumToks, DisableMacroExpansion, OwnsTokens, *this);
    } else {
      TokLexer = std::move(TokenLexerCache[--NumCachedTokenLexers]);
      TokLexer->Init(Toks, NumToks, DisableMacroExpansion, OwnsTokens);
    }
  
    // Save our current state.
    PushIncludeMacroStack();
    CurDirLookup = nullptr;
    CurTokenLexer = std::move(TokLexer);
    if (CurLexerKind != CLK_LexAfterModuleImport)
      CurLexerKind = CLK_TokenLexer;
  }
  
  /// \brief Compute the relative path that names the given file relative to
  /// the given directory.
  static void computeRelativePath(FileManager &FM, const DirectoryEntry *Dir,
                                  const FileEntry *File,
                                  SmallString<128> &Result) {
    Result.clear();
  
    StringRef FilePath = File->getDir()->getName();
    StringRef Path = FilePath;
    while (!Path.empty()) {
      if (const DirectoryEntry *CurDir = FM.getDirectory(Path)) {
        if (CurDir == Dir) {
          Result = FilePath.substr(Path.size());
          llvm::sys::path::append(Result, 
                                  llvm::sys::path::filename(File->getName()));
          return;
        }
      }
      
      Path = llvm::sys::path::parent_path(Path);
    }
    
    Result = File->getName();
  }
  
  void Preprocessor::PropagateLineStartLeadingSpaceInfo(Token &Result) {
    if (CurTokenLexer) {
      CurTokenLexer->PropagateLineStartLeadingSpaceInfo(Result);
      return;
    }
    if (CurLexer) {
      CurLexer->PropagateLineStartLeadingSpaceInfo(Result);
      return;
    }
    // FIXME: Handle other kinds of lexers?  It generally shouldn't matter,
    // but it might if they're empty?
  }
  
  /// \brief Determine the location to use as the end of the buffer for a lexer.
  ///
  /// If the file ends with a newline, form the EOF token on the newline itself,
  /// rather than "on the line following it", which doesn't exist.  This makes
  /// diagnostics relating to the end of file include the last file that the user
  /// actually typed, which is goodness.
  const char *Preprocessor::getCurLexerEndPos() {
    const char *EndPos = CurLexer->BufferEnd;
    if (EndPos != CurLexer->BufferStart &&
        (EndPos[-1] == '\n' || EndPos[-1] == '\r')) {
      --EndPos;
  
      // Handle \n\r and \r\n:
      if (EndPos != CurLexer->BufferStart &&
          (EndPos[-1] == '\n' || EndPos[-1] == '\r') &&
          EndPos[-1] != EndPos[0])
        --EndPos;
    }
  
    return EndPos;
  }
  
  
  /// HandleEndOfFile - This callback is invoked when the lexer hits the end of
  /// the current file.  This either returns the EOF token or pops a level off
  /// the include stack and keeps going.
  bool Preprocessor::HandleEndOfFile(Token &Result, bool isEndOfMacro) {
    assert(!CurTokenLexer &&
           "Ending a file when currently in a macro!");
  
    // See if this file had a controlling macro.
    if (CurPPLexer) {  // Not ending a macro, ignore it.
      if (const IdentifierInfo *ControllingMacro =
            CurPPLexer->MIOpt.GetControllingMacroAtEndOfFile()) {
        // Okay, this has a controlling macro, remember in HeaderFileInfo.
        if (const FileEntry *FE =
              SourceMgr.getFileEntryForID(CurPPLexer->getFileID())) {
          HeaderInfo.SetFileControllingMacro(FE, ControllingMacro);
          if (MacroInfo *MI =
                getMacroInfo(const_cast<IdentifierInfo*>(ControllingMacro))) {
            MI->UsedForHeaderGuard = true;
          }
          if (const IdentifierInfo *DefinedMacro =
                CurPPLexer->MIOpt.GetDefinedMacro()) {
            if (!isMacroDefined(ControllingMacro) &&
                DefinedMacro != ControllingMacro &&
                HeaderInfo.FirstTimeLexingFile(FE)) {
  
              // If the edit distance between the two macros is more than 50%,
              // DefinedMacro may not be header guard, or can be header guard of
              // another header file. Therefore, it maybe defining something
              // completely different. This can be observed in the wild when
              // handling feature macros or header guards in different files.
  
              const StringRef ControllingMacroName = ControllingMacro->getName();
              const StringRef DefinedMacroName = DefinedMacro->getName();
              const size_t MaxHalfLength = std::max(ControllingMacroName.size(),
                                                    DefinedMacroName.size()) / 2;
              const unsigned ED = ControllingMacroName.edit_distance(
                  DefinedMacroName, true, MaxHalfLength);
              if (ED <= MaxHalfLength) {
                // Emit a warning for a bad header guard.
                Diag(CurPPLexer->MIOpt.GetMacroLocation(),
                     diag::warn_header_guard)
                    << CurPPLexer->MIOpt.GetMacroLocation() << ControllingMacro;
                Diag(CurPPLexer->MIOpt.GetDefinedLocation(),
                     diag::note_header_guard)
                    << CurPPLexer->MIOpt.GetDefinedLocation() << DefinedMacro
                    << ControllingMacro
                    << FixItHint::CreateReplacement(
                           CurPPLexer->MIOpt.GetDefinedLocation(),
                           ControllingMacro->getName());
              }
            }
          }
        }
      }
    }
  
    // Complain about reaching a true EOF within arc_cf_code_audited.
    // We don't want to complain about reaching the end of a macro
    // instantiation or a _Pragma.
    if (PragmaARCCFCodeAuditedLoc.isValid() &&
        !isEndOfMacro && !(CurLexer && CurLexer->Is_PragmaLexer)) {
      Diag(PragmaARCCFCodeAuditedLoc, diag::err_pp_eof_in_arc_cf_code_audited);
  
      // Recover by leaving immediately.
      PragmaARCCFCodeAuditedLoc = SourceLocation();
    }
  
    // Complain about reaching a true EOF within assume_nonnull.
    // We don't want to complain about reaching the end of a macro
    // instantiation or a _Pragma.
    if (PragmaAssumeNonNullLoc.isValid() &&
        !isEndOfMacro && !(CurLexer && CurLexer->Is_PragmaLexer)) {
      Diag(PragmaAssumeNonNullLoc, diag::err_pp_eof_in_assume_nonnull);
  
      // Recover by leaving immediately.
      PragmaAssumeNonNullLoc = SourceLocation();
    }
  
    // If this is a #include'd file, pop it off the include stack and continue
    // lexing the #includer file.
    if (!IncludeMacroStack.empty()) {
  
      // If we lexed the code-completion file, act as if we reached EOF.
      if (isCodeCompletionEnabled() && CurPPLexer &&
          SourceMgr.getLocForStartOfFile(CurPPLexer->getFileID()) ==
              CodeCompletionFileLoc) {
        if (CurLexer) {
          Result.startToken();
          CurLexer->FormTokenWithChars(Result, CurLexer->BufferEnd, tok::eof);
          CurLexer.reset();
        } else {
          assert(CurPTHLexer && "Got EOF but no current lexer set!");
          CurPTHLexer->getEOF(Result);
          CurPTHLexer.reset();
        }
  
        CurPPLexer = nullptr;
        return true;
      }
  
      if (!isEndOfMacro && CurPPLexer &&
          SourceMgr.getIncludeLoc(CurPPLexer->getFileID()).isValid()) {
        // Notify SourceManager to record the number of FileIDs that were created
        // during lexing of the #include'd file.
        unsigned NumFIDs =
            SourceMgr.local_sloc_entry_size() -
            CurPPLexer->getInitialNumSLocEntries() + 1/*#include'd file*/;
        SourceMgr.setNumCreatedFIDsForFileID(CurPPLexer->getFileID(), NumFIDs);
      }
  
      FileID ExitedFID;
      if (Callbacks && !isEndOfMacro && CurPPLexer)
        ExitedFID = CurPPLexer->getFileID();
  
      bool LeavingSubmodule = CurSubmodule && CurLexer;
      if (LeavingSubmodule) {
        // Notify the parser that we've left the module.
        const char *EndPos = getCurLexerEndPos();
        Result.startToken();
        CurLexer->BufferPtr = EndPos;
        CurLexer->FormTokenWithChars(Result, EndPos, tok::annot_module_end);
        Result.setAnnotationEndLoc(Result.getLocation());
        Result.setAnnotationValue(CurSubmodule);
  
        // We're done with this submodule.
        LeaveSubmodule();
      }
  
      // We're done with the #included file.
      RemoveTopOfLexerStack();
  
      // Propagate info about start-of-line/leading white-space/etc.
      PropagateLineStartLeadingSpaceInfo(Result);
  
      // Notify the client, if desired, that we are in a new source file.
      if (Callbacks && !isEndOfMacro && CurPPLexer) {
        SrcMgr::CharacteristicKind FileType =
          SourceMgr.getFileCharacteristic(CurPPLexer->getSourceLocation());
        Callbacks->FileChanged(CurPPLexer->getSourceLocation(),
                               PPCallbacks::ExitFile, FileType, ExitedFID);
      }
  
      // Client should lex another token unless we generated an EOM.
      return LeavingSubmodule;
    }
  
    // If this is the end of the main file, form an EOF token.
    if (CurLexer) {
      const char *EndPos = getCurLexerEndPos();
      Result.startToken();
      CurLexer->BufferPtr = EndPos;
      CurLexer->FormTokenWithChars(Result, EndPos, tok::eof);
  
      if (isCodeCompletionEnabled()) {
        // Inserting the code-completion point increases the source buffer by 1,
        // but the main FileID was created before inserting the point.
        // Compensate by reducing the EOF location by 1, otherwise the location
        // will point to the next FileID.
        // FIXME: This is hacky, the code-completion point should probably be
        // inserted before the main FileID is created.
        if (CurLexer->getFileLoc() == CodeCompletionFileLoc)
          Result.setLocation(Result.getLocation().getLocWithOffset(-1));
      }
  
      if (!isIncrementalProcessingEnabled())
        // We're done with lexing.
        CurLexer.reset();
    } else {
      assert(CurPTHLexer && "Got EOF but no current lexer set!");
      CurPTHLexer->getEOF(Result);
      CurPTHLexer.reset();
    }
    
    if (!isIncrementalProcessingEnabled())
      CurPPLexer = nullptr;
  
    if (TUKind == TU_Complete) {
      // This is the end of the top-level file. 'WarnUnusedMacroLocs' has
      // collected all macro locations that we need to warn because they are not
      // used.
      for (WarnUnusedMacroLocsTy::iterator
             I=WarnUnusedMacroLocs.begin(), E=WarnUnusedMacroLocs.end();
             I!=E; ++I)
        Diag(*I, diag::pp_macro_not_used);
    }
  
    // If we are building a module that has an umbrella header, make sure that
    // each of the headers within the directory covered by the umbrella header
    // was actually included by the umbrella header.
    if (Module *Mod = getCurrentModule()) {
      if (Mod->getUmbrellaHeader()) {
        SourceLocation StartLoc
          = SourceMgr.getLocForStartOfFile(SourceMgr.getMainFileID());
  
        if (!getDiagnostics().isIgnored(diag::warn_uncovered_module_header,
                                        StartLoc)) {
          ModuleMap &ModMap = getHeaderSearchInfo().getModuleMap();
          const DirectoryEntry *Dir = Mod->getUmbrellaDir().Entry;
          vfs::FileSystem &FS = *FileMgr.getVirtualFileSystem();
          std::error_code EC;
          for (vfs::recursive_directory_iterator Entry(FS, Dir->getName(), EC), End;
               Entry != End && !EC; Entry.increment(EC)) {
            using llvm::StringSwitch;
            
            // Check whether this entry has an extension typically associated with
            // headers.
            if (!StringSwitch<bool>(llvm::sys::path::extension(Entry->getName()))
                   .Cases(".h", ".H", ".hh", ".hpp", true)
                   .Default(false))
              continue;
  
            if (const FileEntry *Header =
                    getFileManager().getFile(Entry->getName()))
              if (!getSourceManager().hasFileInfo(Header)) {
                if (!ModMap.isHeaderInUnavailableModule(Header)) {
                  // Find the relative path that would access this header.
                  SmallString<128> RelativePath;
                  computeRelativePath(FileMgr, Dir, Header, RelativePath);              
                  Diag(StartLoc, diag::warn_uncovered_module_header)
                    << Mod->getFullModuleName() << RelativePath;
                }
              }
          }
        }
      }
    }
  
    return true;
  }
  
  /// HandleEndOfTokenLexer - This callback is invoked when the current TokenLexer
  /// hits the end of its token stream.
  bool Preprocessor::HandleEndOfTokenLexer(Token &Result) {
    assert(CurTokenLexer && !CurPPLexer &&
           "Ending a macro when currently in a #include file!");
  
    if (!MacroExpandingLexersStack.empty() &&
        MacroExpandingLexersStack.back().first == CurTokenLexer.get())
      removeCachedMacroExpandedTokensOfLastLexer();
  
    // Delete or cache the now-dead macro expander.
    if (NumCachedTokenLexers == TokenLexerCacheSize)
      CurTokenLexer.reset();
    else
      TokenLexerCache[NumCachedTokenLexers++] = std::move(CurTokenLexer);
  
    // Handle this like a #include file being popped off the stack.
    return HandleEndOfFile(Result, true);
  }
  
  /// RemoveTopOfLexerStack - Pop the current lexer/macro exp off the top of the
  /// lexer stack.  This should only be used in situations where the current
  /// state of the top-of-stack lexer is unknown.
  void Preprocessor::RemoveTopOfLexerStack() {
    assert(!IncludeMacroStack.empty() && "Ran out of stack entries to load");
  
    if (CurTokenLexer) {
      // Delete or cache the now-dead macro expander.
      if (NumCachedTokenLexers == TokenLexerCacheSize)
        CurTokenLexer.reset();
      else
        TokenLexerCache[NumCachedTokenLexers++] = std::move(CurTokenLexer);
    }
  
    PopIncludeMacroStack();
  }
  
  /// HandleMicrosoftCommentPaste - When the macro expander pastes together a
  /// comment (/##/) in microsoft mode, this method handles updating the current
  /// state, returning the token on the next source line.
  void Preprocessor::HandleMicrosoftCommentPaste(Token &Tok) {
    assert(CurTokenLexer && !CurPPLexer &&
           "Pasted comment can only be formed from macro");
  
    // We handle this by scanning for the closest real lexer, switching it to
    // raw mode and preprocessor mode.  This will cause it to return \n as an
    // explicit EOD token.
    PreprocessorLexer *FoundLexer = nullptr;
    bool LexerWasInPPMode = false;
    for (unsigned i = 0, e = IncludeMacroStack.size(); i != e; ++i) {
      IncludeStackInfo &ISI = *(IncludeMacroStack.end()-i-1);
      if (ISI.ThePPLexer == nullptr) continue;  // Scan for a real lexer.
  
      // Once we find a real lexer, mark it as raw mode (disabling macro
      // expansions) and preprocessor mode (return EOD).  We know that the lexer
      // was *not* in raw mode before, because the macro that the comment came
      // from was expanded.  However, it could have already been in preprocessor
      // mode (#if COMMENT) in which case we have to return it to that mode and
      // return EOD.
      FoundLexer = ISI.ThePPLexer;
      FoundLexer->LexingRawMode = true;
      LexerWasInPPMode = FoundLexer->ParsingPreprocessorDirective;
      FoundLexer->ParsingPreprocessorDirective = true;
      break;
    }
  
    // Okay, we either found and switched over the lexer, or we didn't find a
    // lexer.  In either case, finish off the macro the comment came from, getting
    // the next token.
    if (!HandleEndOfTokenLexer(Tok)) Lex(Tok);
  
    // Discarding comments as long as we don't have EOF or EOD.  This 'comments
    // out' the rest of the line, including any tokens that came from other macros
    // that were active, as in:
    //  #define submacro a COMMENT b
    //    submacro c
    // which should lex to 'a' only: 'b' and 'c' should be removed.
    while (Tok.isNot(tok::eod) && Tok.isNot(tok::eof))
      Lex(Tok);
  
    // If we got an eod token, then we successfully found the end of the line.
    if (Tok.is(tok::eod)) {
      assert(FoundLexer && "Can't get end of line without an active lexer");
      // Restore the lexer back to normal mode instead of raw mode.
      FoundLexer->LexingRawMode = false;
  
      // If the lexer was already in preprocessor mode, just return the EOD token
      // to finish the preprocessor line.
      if (LexerWasInPPMode) return;
  
      // Otherwise, switch out of PP mode and return the next lexed token.
      FoundLexer->ParsingPreprocessorDirective = false;
      return Lex(Tok);
    }
  
    // If we got an EOF token, then we reached the end of the token stream but
    // didn't find an explicit \n.  This can only happen if there was no lexer
    // active (an active lexer would return EOD at EOF if there was no \n in
    // preprocessor directive mode), so just return EOF as our token.
    assert(!FoundLexer && "Lexer should return EOD before EOF in PP mode");
  }
  
  void Preprocessor::EnterSubmodule(Module *M, SourceLocation ImportLoc) {
    if (!getLangOpts().ModulesLocalVisibility) {
      // Just track that we entered this submodule.
      BuildingSubmoduleStack.push_back(
          BuildingSubmoduleInfo(M, ImportLoc, CurSubmoduleState));
      return;
    }
  
    // Resolve as much of the module definition as we can now, before we enter
    // one of its headers.
    // FIXME: Can we enable Complain here?
    // FIXME: Can we do this when local visibility is disabled?
    ModuleMap &ModMap = getHeaderSearchInfo().getModuleMap();
    ModMap.resolveExports(M, /*Complain=*/false);
    ModMap.resolveUses(M, /*Complain=*/false);
    ModMap.resolveConflicts(M, /*Complain=*/false);
  
    // If this is the first time we've entered this module, set up its state.
    auto R = Submodules.insert(std::make_pair(M, SubmoduleState()));
    auto &State = R.first->second;
    bool FirstTime = R.second;
    if (FirstTime) {
      // Determine the set of starting macros for this submodule; take these
      // from the "null" module (the predefines buffer).
      //
      // FIXME: If we have local visibility but not modules enabled, the
      // NullSubmoduleState is polluted by #defines in the top-level source
      // file.
      auto &StartingMacros = NullSubmoduleState.Macros;
  
      // Restore to the starting state.
      // FIXME: Do this lazily, when each macro name is first referenced.
      for (auto &Macro : StartingMacros) {
        // Skip uninteresting macros.
        if (!Macro.second.getLatest() &&
            Macro.second.getOverriddenMacros().empty())
          continue;
  
        MacroState MS(Macro.second.getLatest());
        MS.setOverriddenMacros(*this, Macro.second.getOverriddenMacros());
        State.Macros.insert(std::make_pair(Macro.first, std::move(MS)));
      }
    }
  
    // Track that we entered this module.
    BuildingSubmoduleStack.push_back(
        BuildingSubmoduleInfo(M, ImportLoc, CurSubmoduleState));
  
    // Switch to this submodule as the current submodule.
    CurSubmoduleState = &State;
  
    // This module is visible to itself.
    if (FirstTime)
      makeModuleVisible(M, ImportLoc);
  }
  
  void Preprocessor::LeaveSubmodule() {
    auto &Info = BuildingSubmoduleStack.back();
  
    Module *LeavingMod = Info.M;
    SourceLocation ImportLoc = Info.ImportLoc;
  
    // Create ModuleMacros for any macros defined in this submodule.
    for (auto &Macro : CurSubmoduleState->Macros) {
      auto *II = const_cast<IdentifierInfo*>(Macro.first);
  
      // Find the starting point for the MacroDirective chain in this submodule.
      MacroDirective *OldMD = nullptr;
      if (getLangOpts().ModulesLocalVisibility) {
        // FIXME: It'd be better to start at the state from when we most recently
        // entered this submodule, but it doesn't really matter.
        auto &PredefMacros = NullSubmoduleState.Macros;
        auto PredefMacroIt = PredefMacros.find(Macro.first);
        if (PredefMacroIt == PredefMacros.end())
          OldMD = nullptr;
        else
          OldMD = PredefMacroIt->second.getLatest();
      }
  
      // This module may have exported a new macro. If so, create a ModuleMacro
      // representing that fact.
      bool ExplicitlyPublic = false;
      for (auto *MD = Macro.second.getLatest(); MD != OldMD;
           MD = MD->getPrevious()) {
        assert(MD && "broken macro directive chain");
  
        // Stop on macros defined in other submodules we #included along the way.
        // There's no point doing this if we're tracking local submodule
        // visibility, since there can be no such directives in our list.
        if (!getLangOpts().ModulesLocalVisibility) {
          Module *Mod = getModuleContainingLocation(MD->getLocation());
          if (Mod != LeavingMod)
            break;
        }
  
        if (auto *VisMD = dyn_cast<VisibilityMacroDirective>(MD)) {
          // The latest visibility directive for a name in a submodule affects
          // all the directives that come before it.
          if (VisMD->isPublic())
            ExplicitlyPublic = true;
          else if (!ExplicitlyPublic)
            // Private with no following public directive: not exported.
            break;
        } else {
          MacroInfo *Def = nullptr;
          if (DefMacroDirective *DefMD = dyn_cast<DefMacroDirective>(MD))
            Def = DefMD->getInfo();
  
          // FIXME: Issue a warning if multiple headers for the same submodule
          // define a macro, rather than silently ignoring all but the first.
          bool IsNew;
          // Don't bother creating a module macro if it would represent a #undef
          // that doesn't override anything.
          if (Def || !Macro.second.getOverriddenMacros().empty())
            addModuleMacro(LeavingMod, II, Def,
                           Macro.second.getOverriddenMacros(), IsNew);
          break;
        }
      }
    }
  
    // FIXME: Before we leave this submodule, we should parse all the other
    // headers within it. Otherwise, we're left with an inconsistent state
    // where we've made the module visible but don't yet have its complete
    // contents.
  
    // Put back the outer module's state, if we're tracking it.
    if (getLangOpts().ModulesLocalVisibility)
      CurSubmoduleState = Info.OuterSubmoduleState;
  
    BuildingSubmoduleStack.pop_back();
  
    // A nested #include makes the included submodule visible.
    makeModuleVisible(LeavingMod, ImportLoc);
  }
  