brintos

brintos / llvm-project-archived public Read only

0
0
Text · 24.8 KiB · 1462058 Raw
579 lines · cpp
1//===--- InclusionRewriter.cpp - Rewrite includes into their expansions ---===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This code rewrites include invocations into their expansions.  This gives you10// a file with all included files merged into it.11//12//===----------------------------------------------------------------------===//13 14#include "clang/Rewrite/Frontend/Rewriters.h"15#include "clang/Basic/SourceManager.h"16#include "clang/Frontend/PreprocessorOutputOptions.h"17#include "clang/Lex/Pragma.h"18#include "clang/Lex/Preprocessor.h"19#include "llvm/ADT/SmallString.h"20#include "llvm/Support/raw_ostream.h"21#include <optional>22 23using namespace clang;24using namespace llvm;25 26namespace {27 28class InclusionRewriter : public PPCallbacks {29  /// Information about which #includes were actually performed,30  /// created by preprocessor callbacks.31  struct IncludedFile {32    FileID Id;33    SrcMgr::CharacteristicKind FileType;34    IncludedFile(FileID Id, SrcMgr::CharacteristicKind FileType)35        : Id(Id), FileType(FileType) {}36  };37  Preprocessor &PP; ///< Used to find inclusion directives.38  SourceManager &SM; ///< Used to read and manage source files.39  raw_ostream &OS; ///< The destination stream for rewritten contents.40  StringRef MainEOL; ///< The line ending marker to use.41  llvm::MemoryBufferRef PredefinesBuffer; ///< The preprocessor predefines.42  bool ShowLineMarkers; ///< Show #line markers.43  bool UseLineDirectives; ///< Use of line directives or line markers.44  /// Tracks where inclusions that change the file are found.45  std::map<SourceLocation, IncludedFile> FileIncludes;46  /// Tracks where inclusions that import modules are found.47  std::map<SourceLocation, const Module *> ModuleIncludes;48  /// Tracks where inclusions that enter modules (in a module build) are found.49  std::map<SourceLocation, const Module *> ModuleEntryIncludes;50  /// Tracks where #if and #elif directives get evaluated and whether to true.51  std::map<SourceLocation, bool> IfConditions;52  /// Used transitively for building up the FileIncludes mapping over the53  /// various \c PPCallbacks callbacks.54  SourceLocation LastInclusionLocation;55public:56  InclusionRewriter(Preprocessor &PP, raw_ostream &OS, bool ShowLineMarkers,57                    bool UseLineDirectives);58  void Process(FileID FileId, SrcMgr::CharacteristicKind FileType);59  void setPredefinesBuffer(const llvm::MemoryBufferRef &Buf) {60    PredefinesBuffer = Buf;61  }62  void detectMainFileEOL();63  void handleModuleBegin(Token &Tok) {64    assert(Tok.getKind() == tok::annot_module_begin);65    ModuleEntryIncludes.insert(66        {Tok.getLocation(), (Module *)Tok.getAnnotationValue()});67  }68private:69  void FileChanged(SourceLocation Loc, FileChangeReason Reason,70                   SrcMgr::CharacteristicKind FileType,71                   FileID PrevFID) override;72  void FileSkipped(const FileEntryRef &SkippedFile, const Token &FilenameTok,73                   SrcMgr::CharacteristicKind FileType) override;74  void InclusionDirective(SourceLocation HashLoc, const Token &IncludeTok,75                          StringRef FileName, bool IsAngled,76                          CharSourceRange FilenameRange,77                          OptionalFileEntryRef File, StringRef SearchPath,78                          StringRef RelativePath, const Module *SuggestedModule,79                          bool ModuleImported,80                          SrcMgr::CharacteristicKind FileType) override;81  void If(SourceLocation Loc, SourceRange ConditionRange,82          ConditionValueKind ConditionValue) override;83  void Elif(SourceLocation Loc, SourceRange ConditionRange,84            ConditionValueKind ConditionValue, SourceLocation IfLoc) override;85  void WriteLineInfo(StringRef Filename, int Line,86                     SrcMgr::CharacteristicKind FileType,87                     StringRef Extra = StringRef());88  void WriteImplicitModuleImport(const Module *Mod);89  void OutputContentUpTo(const MemoryBufferRef &FromFile, unsigned &WriteFrom,90                         unsigned WriteTo, StringRef EOL, int &lines,91                         bool EnsureNewline);92  void CommentOutDirective(Lexer &DirectivesLex, const Token &StartToken,93                           const MemoryBufferRef &FromFile, StringRef EOL,94                           unsigned &NextToWrite, int &Lines,95                           const IncludedFile *Inc = nullptr);96  const IncludedFile *FindIncludeAtLocation(SourceLocation Loc) const;97  StringRef getIncludedFileName(const IncludedFile *Inc) const;98  const Module *FindModuleAtLocation(SourceLocation Loc) const;99  const Module *FindEnteredModule(SourceLocation Loc) const;100  bool IsIfAtLocationTrue(SourceLocation Loc) const;101  StringRef NextIdentifierName(Lexer &RawLex, Token &RawToken);102};103 104}  // end anonymous namespace105 106/// Initializes an InclusionRewriter with a \p PP source and \p OS destination.107InclusionRewriter::InclusionRewriter(Preprocessor &PP, raw_ostream &OS,108                                     bool ShowLineMarkers,109                                     bool UseLineDirectives)110    : PP(PP), SM(PP.getSourceManager()), OS(OS), MainEOL("\n"),111      ShowLineMarkers(ShowLineMarkers), UseLineDirectives(UseLineDirectives),112      LastInclusionLocation(SourceLocation()) {}113 114/// Write appropriate line information as either #line directives or GNU line115/// markers depending on what mode we're in, including the \p Filename and116/// \p Line we are located at, using the specified \p EOL line separator, and117/// any \p Extra context specifiers in GNU line directives.118void InclusionRewriter::WriteLineInfo(StringRef Filename, int Line,119                                      SrcMgr::CharacteristicKind FileType,120                                      StringRef Extra) {121  if (!ShowLineMarkers)122    return;123  if (UseLineDirectives) {124    OS << "#line" << ' ' << Line << ' ' << '"';125    OS.write_escaped(Filename);126    OS << '"';127  } else {128    // Use GNU linemarkers as described here:129    // http://gcc.gnu.org/onlinedocs/cpp/Preprocessor-Output.html130    OS << '#' << ' ' << Line << ' ' << '"';131    OS.write_escaped(Filename);132    OS << '"';133    if (!Extra.empty())134      OS << Extra;135    if (FileType == SrcMgr::C_System)136      // "`3' This indicates that the following text comes from a system header137      // file, so certain warnings should be suppressed."138      OS << " 3";139    else if (FileType == SrcMgr::C_ExternCSystem)140      // as above for `3', plus "`4' This indicates that the following text141      // should be treated as being wrapped in an implicit extern "C" block."142      OS << " 3 4";143  }144  OS << MainEOL;145}146 147void InclusionRewriter::WriteImplicitModuleImport(const Module *Mod) {148  OS << "#pragma clang module import " << Mod->getFullModuleName(true)149     << " /* clang -frewrite-includes: implicit import */" << MainEOL;150}151 152/// FileChanged - Whenever the preprocessor enters or exits a #include file153/// it invokes this handler.154void InclusionRewriter::FileChanged(SourceLocation Loc,155                                    FileChangeReason Reason,156                                    SrcMgr::CharacteristicKind NewFileType,157                                    FileID) {158  if (Reason != EnterFile)159    return;160  if (LastInclusionLocation.isInvalid())161    // we didn't reach this file (eg: the main file) via an inclusion directive162    return;163  FileID Id = FullSourceLoc(Loc, SM).getFileID();164  auto P = FileIncludes.insert(165      std::make_pair(LastInclusionLocation, IncludedFile(Id, NewFileType)));166  (void)P;167  assert(P.second && "Unexpected revisitation of the same include directive");168  LastInclusionLocation = SourceLocation();169}170 171/// Called whenever an inclusion is skipped due to canonical header protection172/// macros.173void InclusionRewriter::FileSkipped(const FileEntryRef & /*SkippedFile*/,174                                    const Token & /*FilenameTok*/,175                                    SrcMgr::CharacteristicKind /*FileType*/) {176  assert(LastInclusionLocation.isValid() &&177         "A file, that wasn't found via an inclusion directive, was skipped");178  LastInclusionLocation = SourceLocation();179}180 181/// This should be called whenever the preprocessor encounters include182/// directives. It does not say whether the file has been included, but it183/// provides more information about the directive (hash location instead184/// of location inside the included file). It is assumed that the matching185/// FileChanged() or FileSkipped() is called after this (or neither is186/// called if this #include results in an error or does not textually include187/// anything).188void InclusionRewriter::InclusionDirective(189    SourceLocation HashLoc, const Token & /*IncludeTok*/,190    StringRef /*FileName*/, bool /*IsAngled*/,191    CharSourceRange /*FilenameRange*/, OptionalFileEntryRef /*File*/,192    StringRef /*SearchPath*/, StringRef /*RelativePath*/,193    const Module *SuggestedModule, bool ModuleImported,194    SrcMgr::CharacteristicKind FileType) {195  if (ModuleImported) {196    auto P = ModuleIncludes.insert(std::make_pair(HashLoc, SuggestedModule));197    (void)P;198    assert(P.second && "Unexpected revisitation of the same include directive");199  } else200    LastInclusionLocation = HashLoc;201}202 203void InclusionRewriter::If(SourceLocation Loc, SourceRange ConditionRange,204                           ConditionValueKind ConditionValue) {205  auto P = IfConditions.insert(std::make_pair(Loc, ConditionValue == CVK_True));206  (void)P;207  assert(P.second && "Unexpected revisitation of the same if directive");208}209 210void InclusionRewriter::Elif(SourceLocation Loc, SourceRange ConditionRange,211                             ConditionValueKind ConditionValue,212                             SourceLocation IfLoc) {213  auto P = IfConditions.insert(std::make_pair(Loc, ConditionValue == CVK_True));214  (void)P;215  assert(P.second && "Unexpected revisitation of the same elif directive");216}217 218/// Simple lookup for a SourceLocation (specifically one denoting the hash in219/// an inclusion directive) in the map of inclusion information, FileChanges.220const InclusionRewriter::IncludedFile *221InclusionRewriter::FindIncludeAtLocation(SourceLocation Loc) const {222  const auto I = FileIncludes.find(Loc);223  if (I != FileIncludes.end())224    return &I->second;225  return nullptr;226}227 228/// Simple lookup for a SourceLocation (specifically one denoting the hash in229/// an inclusion directive) in the map of module inclusion information.230const Module *231InclusionRewriter::FindModuleAtLocation(SourceLocation Loc) const {232  const auto I = ModuleIncludes.find(Loc);233  if (I != ModuleIncludes.end())234    return I->second;235  return nullptr;236}237 238/// Simple lookup for a SourceLocation (specifically one denoting the hash in239/// an inclusion directive) in the map of module entry information.240const Module *241InclusionRewriter::FindEnteredModule(SourceLocation Loc) const {242  const auto I = ModuleEntryIncludes.find(Loc);243  if (I != ModuleEntryIncludes.end())244    return I->second;245  return nullptr;246}247 248bool InclusionRewriter::IsIfAtLocationTrue(SourceLocation Loc) const {249  const auto I = IfConditions.find(Loc);250  if (I != IfConditions.end())251    return I->second;252  return false;253}254 255void InclusionRewriter::detectMainFileEOL() {256  std::optional<MemoryBufferRef> FromFile =257      *SM.getBufferOrNone(SM.getMainFileID());258  assert(FromFile);259  if (!FromFile)260    return; // Should never happen, but whatever.261  MainEOL = FromFile->getBuffer().detectEOL();262}263 264/// Writes out bytes from \p FromFile, starting at \p NextToWrite and ending at265/// \p WriteTo - 1.266void InclusionRewriter::OutputContentUpTo(const MemoryBufferRef &FromFile,267                                          unsigned &WriteFrom, unsigned WriteTo,268                                          StringRef LocalEOL, int &Line,269                                          bool EnsureNewline) {270  if (WriteTo <= WriteFrom)271    return;272  if (FromFile == PredefinesBuffer) {273    // Ignore the #defines of the predefines buffer.274    WriteFrom = WriteTo;275    return;276  }277 278  // If we would output half of a line ending, advance one character to output279  // the whole line ending.  All buffers are null terminated, so looking ahead280  // one byte is safe.281  if (LocalEOL.size() == 2 &&282      LocalEOL[0] == (FromFile.getBufferStart() + WriteTo)[-1] &&283      LocalEOL[1] == (FromFile.getBufferStart() + WriteTo)[0])284    WriteTo++;285 286  StringRef TextToWrite(FromFile.getBufferStart() + WriteFrom,287                        WriteTo - WriteFrom);288  // count lines manually, it's faster than getPresumedLoc()289  Line += TextToWrite.count(LocalEOL);290 291  if (MainEOL == LocalEOL) {292    OS << TextToWrite;293  } else {294    // Output the file one line at a time, rewriting the line endings as we go.295    StringRef Rest = TextToWrite;296    while (!Rest.empty()) {297      // Identify and output the next line excluding an EOL sequence if present.298      size_t Idx = Rest.find(LocalEOL);299      StringRef LineText = Rest.substr(0, Idx);300      OS << LineText;301      if (Idx != StringRef::npos) {302        // An EOL sequence was present, output the EOL sequence for the303        // main source file and skip past the local EOL sequence.304        OS << MainEOL;305        Idx += LocalEOL.size();306      }307      // Strip the line just handled. If Idx is npos or matches the end of the308      // text, Rest will be set to an empty string and the loop will terminate.309      Rest = Rest.substr(Idx);310    }311  }312  if (EnsureNewline && !TextToWrite.ends_with(LocalEOL))313    OS << MainEOL;314 315  WriteFrom = WriteTo;316}317 318StringRef319InclusionRewriter::getIncludedFileName(const IncludedFile *Inc) const {320  if (Inc) {321    auto B = SM.getBufferOrNone(Inc->Id);322    assert(B && "Attempting to process invalid inclusion");323    if (B)324      return llvm::sys::path::filename(B->getBufferIdentifier());325  }326  return StringRef();327}328 329/// Print characters from \p FromFile starting at \p NextToWrite up until the330/// inclusion directive at \p StartToken, then print out the inclusion331/// inclusion directive disabled by a #if directive, updating \p NextToWrite332/// and \p Line to track the number of source lines visited and the progress333/// through the \p FromFile buffer.334void InclusionRewriter::CommentOutDirective(Lexer &DirectiveLex,335                                            const Token &StartToken,336                                            const MemoryBufferRef &FromFile,337                                            StringRef LocalEOL,338                                            unsigned &NextToWrite, int &Line,339                                            const IncludedFile *Inc) {340  OutputContentUpTo(FromFile, NextToWrite,341                    SM.getFileOffset(StartToken.getLocation()), LocalEOL, Line,342                    false);343  Token DirectiveToken;344  do {345    DirectiveLex.LexFromRawLexer(DirectiveToken);346  } while (!DirectiveToken.is(tok::eod) && DirectiveToken.isNot(tok::eof));347  if (FromFile == PredefinesBuffer) {348    // OutputContentUpTo() would not output anything anyway.349    return;350  }351  if (Inc) {352    OS << "#if defined(__CLANG_REWRITTEN_INCLUDES) ";353    if (isSystem(Inc->FileType))354      OS << "|| defined(__CLANG_REWRITTEN_SYSTEM_INCLUDES) ";355    OS << "/* " << getIncludedFileName(Inc);356  } else {357    OS << "#if 0 /*";358  }359  OS << " expanded by -frewrite-includes */" << MainEOL;360  OutputContentUpTo(FromFile, NextToWrite,361                    SM.getFileOffset(DirectiveToken.getLocation()) +362                        DirectiveToken.getLength(),363                    LocalEOL, Line, true);364  OS << (Inc ? "#else /* " : "#endif /*") << getIncludedFileName(Inc)365     << " expanded by -frewrite-includes */" << MainEOL;366}367 368/// Find the next identifier in the pragma directive specified by \p RawToken.369StringRef InclusionRewriter::NextIdentifierName(Lexer &RawLex,370                                                Token &RawToken) {371  RawLex.LexFromRawLexer(RawToken);372  if (RawToken.is(tok::raw_identifier))373    PP.LookUpIdentifierInfo(RawToken);374  if (RawToken.is(tok::identifier))375    return RawToken.getIdentifierInfo()->getName();376  return StringRef();377}378 379/// Use a raw lexer to analyze \p FileId, incrementally copying parts of it380/// and including content of included files recursively.381void InclusionRewriter::Process(FileID FileId,382                                SrcMgr::CharacteristicKind FileType) {383  MemoryBufferRef FromFile;384  {385    auto B = SM.getBufferOrNone(FileId);386    assert(B && "Attempting to process invalid inclusion");387    if (B)388      FromFile = *B;389  }390  StringRef FileName = FromFile.getBufferIdentifier();391  Lexer RawLex(FileId, FromFile, PP.getSourceManager(), PP.getLangOpts());392  RawLex.SetCommentRetentionState(false);393 394  StringRef LocalEOL = FromFile.getBuffer().detectEOL();395 396  // Per the GNU docs: "1" indicates entering a new file.397  if (FileId == SM.getMainFileID() || FileId == PP.getPredefinesFileID())398    WriteLineInfo(FileName, 1, FileType, "");399  else400    WriteLineInfo(FileName, 1, FileType, " 1");401 402  if (SM.getFileIDSize(FileId) == 0)403    return;404 405  // The next byte to be copied from the source file, which may be non-zero if406  // the lexer handled a BOM.407  unsigned NextToWrite = SM.getFileOffset(RawLex.getSourceLocation());408  assert(SM.getLineNumber(FileId, NextToWrite) == 1);409  int Line = 1; // The current input file line number.410 411  Token RawToken;412  RawLex.LexFromRawLexer(RawToken);413 414  // TODO: Consider adding a switch that strips possibly unimportant content,415  // such as comments, to reduce the size of repro files.416  while (RawToken.isNot(tok::eof)) {417    if (RawToken.is(tok::hash) && RawToken.isAtStartOfLine()) {418      RawLex.setParsingPreprocessorDirective(true);419      Token HashToken = RawToken;420      RawLex.LexFromRawLexer(RawToken);421      if (RawToken.is(tok::raw_identifier))422        PP.LookUpIdentifierInfo(RawToken);423      if (RawToken.getIdentifierInfo() != nullptr) {424        switch (RawToken.getIdentifierInfo()->getPPKeywordID()) {425          case tok::pp_include:426          case tok::pp_include_next:427          case tok::pp_import: {428            SourceLocation Loc = HashToken.getLocation();429            const IncludedFile *Inc = FindIncludeAtLocation(Loc);430            CommentOutDirective(RawLex, HashToken, FromFile, LocalEOL,431                                NextToWrite, Line, Inc);432            if (FileId != PP.getPredefinesFileID())433              WriteLineInfo(FileName, Line - 1, FileType, "");434            StringRef LineInfoExtra;435            if (const Module *Mod = FindModuleAtLocation(Loc))436              WriteImplicitModuleImport(Mod);437            else if (Inc) {438              const Module *Mod = FindEnteredModule(Loc);439              if (Mod)440                OS << "#pragma clang module begin "441                   << Mod->getFullModuleName(true) << "\n";442 443              // Include and recursively process the file.444              Process(Inc->Id, Inc->FileType);445 446              if (Mod)447                OS << "#pragma clang module end /*"448                   << Mod->getFullModuleName(true) << "*/\n";449              // There's no #include, therefore no #if, for -include files.450              if (FromFile != PredefinesBuffer) {451                OS << "#endif /* " << getIncludedFileName(Inc)452                   << " expanded by -frewrite-includes */" << LocalEOL;453              }454 455              // Add line marker to indicate we're returning from an included456              // file.457              LineInfoExtra = " 2";458            }459            // fix up lineinfo (since commented out directive changed line460            // numbers) for inclusions that were skipped due to header guards461            WriteLineInfo(FileName, Line, FileType, LineInfoExtra);462            break;463          }464          case tok::pp_pragma: {465            StringRef Identifier = NextIdentifierName(RawLex, RawToken);466            if (Identifier == "clang" || Identifier == "GCC") {467              if (NextIdentifierName(RawLex, RawToken) == "system_header") {468                // keep the directive in, commented out469                CommentOutDirective(RawLex, HashToken, FromFile, LocalEOL,470                  NextToWrite, Line);471                // update our own type472                FileType = SM.getFileCharacteristic(RawToken.getLocation());473                WriteLineInfo(FileName, Line, FileType);474              }475            } else if (Identifier == "once") {476              // keep the directive in, commented out477              CommentOutDirective(RawLex, HashToken, FromFile, LocalEOL,478                NextToWrite, Line);479              WriteLineInfo(FileName, Line, FileType);480            }481            break;482          }483          case tok::pp_if:484          case tok::pp_elif: {485            bool elif = (RawToken.getIdentifierInfo()->getPPKeywordID() ==486                         tok::pp_elif);487            bool isTrue = IsIfAtLocationTrue(RawToken.getLocation());488            OutputContentUpTo(FromFile, NextToWrite,489                              SM.getFileOffset(HashToken.getLocation()),490                              LocalEOL, Line, /*EnsureNewline=*/true);491            do {492              RawLex.LexFromRawLexer(RawToken);493            } while (!RawToken.is(tok::eod) && RawToken.isNot(tok::eof));494            // We need to disable the old condition, but that is tricky.495            // Trying to comment it out can easily lead to comment nesting.496            // So instead make the condition harmless by making it enclose497            // and empty block. Moreover, put it itself inside an #if 0 block498            // to disable it from getting evaluated (e.g. __has_include_next499            // warns if used from the primary source file).500            OS << "#if 0 /* disabled by -frewrite-includes */" << MainEOL;501            if (elif) {502              OS << "#if 0" << MainEOL;503            }504            OutputContentUpTo(FromFile, NextToWrite,505                              SM.getFileOffset(RawToken.getLocation()) +506                                  RawToken.getLength(),507                              LocalEOL, Line, /*EnsureNewline=*/true);508            // Close the empty block and the disabling block.509            OS << "#endif" << MainEOL;510            OS << "#endif /* disabled by -frewrite-includes */" << MainEOL;511            OS << (elif ? "#elif " : "#if ") << (isTrue ? "1" : "0")512               << " /* evaluated by -frewrite-includes */" << MainEOL;513            WriteLineInfo(FileName, Line, FileType);514            break;515          }516          case tok::pp_endif:517          case tok::pp_else: {518            // We surround every #include by #if 0 to comment it out, but that519            // changes line numbers. These are fixed up right after that, but520            // the whole #include could be inside a preprocessor conditional521            // that is not processed. So it is necessary to fix the line522            // numbers one the next line after each #else/#endif as well.523            RawLex.SetKeepWhitespaceMode(true);524            do {525              RawLex.LexFromRawLexer(RawToken);526            } while (RawToken.isNot(tok::eod) && RawToken.isNot(tok::eof));527            OutputContentUpTo(FromFile, NextToWrite,528                              SM.getFileOffset(RawToken.getLocation()) +529                                  RawToken.getLength(),530                              LocalEOL, Line, /*EnsureNewline=*/ true);531            WriteLineInfo(FileName, Line, FileType);532            RawLex.SetKeepWhitespaceMode(false);533            break;534          }535          default:536            break;537        }538      }539      RawLex.setParsingPreprocessorDirective(false);540    }541    RawLex.LexFromRawLexer(RawToken);542  }543  OutputContentUpTo(FromFile, NextToWrite,544                    SM.getFileOffset(SM.getLocForEndOfFile(FileId)), LocalEOL,545                    Line, /*EnsureNewline=*/true);546}547 548/// InclusionRewriterInInput - Implement -frewrite-includes mode.549void clang::RewriteIncludesInInput(Preprocessor &PP, raw_ostream *OS,550                                   const PreprocessorOutputOptions &Opts) {551  SourceManager &SM = PP.getSourceManager();552  InclusionRewriter *Rewrite = new InclusionRewriter(553      PP, *OS, Opts.ShowLineMarkers, Opts.UseLineDirectives);554  Rewrite->detectMainFileEOL();555 556  PP.addPPCallbacks(std::unique_ptr<PPCallbacks>(Rewrite));557  PP.IgnorePragmas();558 559  // First let the preprocessor process the entire file and call callbacks.560  // Callbacks will record which #include's were actually performed.561  PP.EnterMainSourceFile();562  Token Tok;563  // Only preprocessor directives matter here, so disable macro expansion564  // everywhere else as an optimization.565  // TODO: It would be even faster if the preprocessor could be switched566  // to a mode where it would parse only preprocessor directives and comments,567  // nothing else matters for parsing or processing.568  PP.SetMacroExpansionOnlyInDirectives();569  do {570    PP.Lex(Tok);571    if (Tok.is(tok::annot_module_begin))572      Rewrite->handleModuleBegin(Tok);573  } while (Tok.isNot(tok::eof));574  Rewrite->setPredefinesBuffer(SM.getBufferOrFake(PP.getPredefinesFileID()));575  Rewrite->Process(PP.getPredefinesFileID(), SrcMgr::C_User);576  Rewrite->Process(SM.getMainFileID(), SrcMgr::C_User);577  OS->flush();578}579