text: //===--- DependencyFile.cpp - Generate dependency file --------------------===//
  //
  // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
  // See https://llvm.org/LICENSE.txt for license information.
  // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
  //
  //===----------------------------------------------------------------------===//
  //
  // This code generates dependency files.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Frontend/Utils.h"
  #include "clang/Basic/FileManager.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Frontend/DependencyOutputOptions.h"
  #include "clang/Frontend/FrontendDiagnostic.h"
  #include "clang/Lex/DirectoryLookup.h"
  #include "clang/Lex/ModuleMap.h"
  #include "clang/Lex/PPCallbacks.h"
  #include "clang/Lex/Preprocessor.h"
  #include "clang/Serialization/ASTReader.h"
  #include "llvm/ADT/StringSet.h"
  #include "llvm/ADT/StringSwitch.h"
  #include "llvm/Support/FileSystem.h"
  #include "llvm/Support/Path.h"
  #include "llvm/Support/raw_ostream.h"
  
  using namespace clang;
  
  namespace {
  struct DepCollectorPPCallbacks : public PPCallbacks {
    DependencyCollector &DepCollector;
    SourceManager &SM;
    DiagnosticsEngine &Diags;
    DepCollectorPPCallbacks(DependencyCollector &L, SourceManager &SM,
                            DiagnosticsEngine &Diags)
        : DepCollector(L), SM(SM), Diags(Diags) {}
  
    void FileChanged(SourceLocation Loc, FileChangeReason Reason,
                     SrcMgr::CharacteristicKind FileType,
                     FileID PrevFID) override {
      if (Reason != PPCallbacks::EnterFile)
        return;
  
      // Dependency generation really does want to go all the way to the
      // file entry for a source location to find out what is depended on.
      // We do not want #line markers to affect dependency generation!
      if (Optional<StringRef> Filename = SM.getNonBuiltinFilenameForID(
              SM.getFileID(SM.getExpansionLoc(Loc))))
        DepCollector.maybeAddDependency(
            llvm::sys::path::remove_leading_dotslash(*Filename),
            /*FromModule*/ false, isSystem(FileType), /*IsModuleFile*/ false,
            /*IsMissing*/ false);
    }
  
    void FileSkipped(const FileEntryRef &SkippedFile, const Token &FilenameTok,
                     SrcMgr::CharacteristicKind FileType) override {
      StringRef Filename =
          llvm::sys::path::remove_leading_dotslash(SkippedFile.getName());
      DepCollector.maybeAddDependency(Filename, /*FromModule=*/false,
                                      /*IsSystem=*/isSystem(FileType),
                                      /*IsModuleFile=*/false,
                                      /*IsMissing=*/false);
    }
  
    void InclusionDirective(SourceLocation HashLoc, const Token &IncludeTok,
                            StringRef FileName, bool IsAngled,
                            CharSourceRange FilenameRange, const FileEntry *File,
                            StringRef SearchPath, StringRef RelativePath,
                            const Module *Imported,
                            SrcMgr::CharacteristicKind FileType) override {
      if (!File)
        DepCollector.maybeAddDependency(FileName, /*FromModule*/false,
                                       /*IsSystem*/false, /*IsModuleFile*/false,
                                       /*IsMissing*/true);
      // Files that actually exist are handled by FileChanged.
    }
  
    void HasInclude(SourceLocation Loc, StringRef SpelledFilename, bool IsAngled,
                    Optional<FileEntryRef> File,
                    SrcMgr::CharacteristicKind FileType) override {
      if (!File)
        return;
      StringRef Filename =
          llvm::sys::path::remove_leading_dotslash(File->getName());
      DepCollector.maybeAddDependency(Filename, /*FromModule=*/false,
                                      /*IsSystem=*/isSystem(FileType),
                                      /*IsModuleFile=*/false,
                                      /*IsMissing=*/false);
    }
  
    void EndOfMainFile() override { DepCollector.finishedMainFile(Diags); }
  };
  
  struct DepCollectorMMCallbacks : public ModuleMapCallbacks {
    DependencyCollector &DepCollector;
    DepCollectorMMCallbacks(DependencyCollector &DC) : DepCollector(DC) {}
  
    void moduleMapFileRead(SourceLocation Loc, const FileEntry &Entry,
                           bool IsSystem) override {
      StringRef Filename = Entry.getName();
      DepCollector.maybeAddDependency(Filename, /*FromModule*/false,
                                      /*IsSystem*/IsSystem,
                                      /*IsModuleFile*/false,
                                      /*IsMissing*/false);
    }
  };
  
  // FIXME: This should not be separate from upstream, but we haven't
  // upstreamed support for SkipUnusedModuleMaps.
  struct DFGMMCallback : public ModuleMapCallbacks {
    DependencyCollector &DepCollector;
    bool SkipUnusedModuleMaps;
    DFGMMCallback(DependencyCollector &DC, bool SkipUnusedModuleMaps)
        : DepCollector(DC), SkipUnusedModuleMaps(SkipUnusedModuleMaps) {}
  
    void moduleMapFileRead(SourceLocation Loc, const FileEntry &Entry,
                           bool IsSystem) override {
      if (SkipUnusedModuleMaps)
        return;
      StringRef Filename = Entry.getName();
      DepCollector.maybeAddDependency(Filename, /*FromModule*/ false,
                                      /*IsSystem*/ IsSystem,
                                      /*IsModuleFile*/ false,
                                      /*IsMissing*/ false);
    }
  
    void moduleMapFoundForModule(const FileEntry &Entry, const Module *M,
                                 bool IsSystem) override {
      if (!SkipUnusedModuleMaps)
        return;
      DepCollector.maybeAddDependency(Entry.getName(), /*FromModule*/ false,
                                      /*IsSystem*/ IsSystem,
                                      /*IsModuleFile*/ false,
                                      /*IsMissing*/ false);
    }
  };
  
  struct DepCollectorASTListener : public ASTReaderListener {
    DependencyCollector &DepCollector;
    DepCollectorASTListener(DependencyCollector &L) : DepCollector(L) { }
    bool needsInputFileVisitation() override { return true; }
    bool needsSystemInputFileVisitation() override {
      return DepCollector.needSystemDependencies();
    }
    void visitModuleFile(StringRef Filename,
                         serialization::ModuleKind Kind) override {
      DepCollector.maybeAddDependency(Filename, /*FromModule*/true,
                                     /*IsSystem*/false, /*IsModuleFile*/true,
                                     /*IsMissing*/false);
    }
    bool visitInputFile(StringRef Filename, bool IsSystem,
                        bool IsOverridden, bool IsExplicitModule) override {
      if (IsOverridden || IsExplicitModule)
        return true;
  
      DepCollector.maybeAddDependency(Filename, /*FromModule*/true, IsSystem,
                                     /*IsModuleFile*/false, /*IsMissing*/false);
      return true;
    }
  };
  } // end anonymous namespace
  
  void DependencyCollector::maybeAddDependency(StringRef Filename,
                                               bool FromModule, bool IsSystem,
                                               bool IsModuleFile,
                                               bool IsMissing) {
    if (sawDependency(Filename, FromModule, IsSystem, IsModuleFile, IsMissing))
      addDependency(Filename);
  }
  
  bool DependencyCollector::addDependency(StringRef Filename) {
    if (Seen.insert(Filename).second) {
      Dependencies.push_back(std::string(Filename));
      return true;
    }
    return false;
  }
  
  static bool isSpecialFilename(StringRef Filename) {
    return llvm::StringSwitch<bool>(Filename)
        .Case("<built-in>", true)
        .Case("<stdin>", true)
        .Default(false);
  }
  
  bool DependencyCollector::sawDependency(StringRef Filename, bool FromModule,
                                          bool IsSystem, bool IsModuleFile,
                                          bool IsMissing) {
    return !isSpecialFilename(Filename) &&
           (needSystemDependencies() || !IsSystem);
  }
  
  DependencyCollector::~DependencyCollector() { }
  void DependencyCollector::attachToPreprocessor(Preprocessor &PP) {
    PP.addPPCallbacks(std::make_unique<DepCollectorPPCallbacks>(
        *this, PP.getSourceManager(), PP.getDiagnostics()));
    PP.getHeaderSearchInfo().getModuleMap().addModuleMapCallbacks(
        std::make_unique<DepCollectorMMCallbacks>(*this));
  }
  void DependencyCollector::attachToASTReader(ASTReader &R) {
    R.addListener(std::make_unique<DepCollectorASTListener>(*this));
  }
  
  DependencyFileGenerator::DependencyFileGenerator(
      const DependencyOutputOptions &Opts)
      : OutputFile(Opts.OutputFile), Targets(Opts.Targets),
        IncludeSystemHeaders(Opts.IncludeSystemHeaders),
        PhonyTarget(Opts.UsePhonyTargets),
        AddMissingHeaderDeps(Opts.AddMissingHeaderDeps), SeenMissingHeader(false),
        IncludeModuleFiles(Opts.IncludeModuleFiles),
        SkipUnusedModuleMaps(Opts.SkipUnusedModuleMaps),
        OutputFormat(Opts.OutputFormat), InputFileIndex(0) {
    for (const auto &ExtraDep : Opts.ExtraDeps) {
      if (addDependency(ExtraDep))
        ++InputFileIndex;
    }
  }
  
  void DependencyFileGenerator::attachToPreprocessor(Preprocessor &PP) {
    // Disable the "file not found" diagnostic if the -MG option was given.
    if (AddMissingHeaderDeps)
      PP.SetSuppressIncludeNotFoundError(true);
  
    // FIXME: Restore the call to DependencyCollector::attachToPreprocessor(PP);
    // once the SkipUnusedModuleMaps is upstreamed.
    PP.addPPCallbacks(std::make_unique<DepCollectorPPCallbacks>(
        *this, PP.getSourceManager(), PP.getDiagnostics()));
    PP.getHeaderSearchInfo().getModuleMap().addModuleMapCallbacks(
        std::make_unique<DFGMMCallback>(*this, SkipUnusedModuleMaps));
  }
  
  bool DependencyFileGenerator::sawDependency(StringRef Filename, bool FromModule,
                                              bool IsSystem, bool IsModuleFile,
                                              bool IsMissing) {
    if (IsMissing) {
      // Handle the case of missing file from an inclusion directive.
      if (AddMissingHeaderDeps)
        return true;
      SeenMissingHeader = true;
      return false;
    }
    if (IsModuleFile && !IncludeModuleFiles)
      return false;
  
    if (isSpecialFilename(Filename))
      return false;
  
    if (IncludeSystemHeaders)
      return true;
  
    return !IsSystem;
  }
  
  void DependencyFileGenerator::finishedMainFile(DiagnosticsEngine &Diags) {
    outputDependencyFile(Diags);
  }
  
  /// Print the filename, with escaping or quoting that accommodates the three
  /// most likely tools that use dependency files: GNU Make, BSD Make, and
  /// NMake/Jom.
  ///
  /// BSD Make is the simplest case: It does no escaping at all.  This means
  /// characters that are normally delimiters, i.e. space and # (the comment
  /// character) simply aren't supported in filenames.
  ///
  /// GNU Make does allow space and # in filenames, but to avoid being treated
  /// as a delimiter or comment, these must be escaped with a backslash. Because
  /// backslash is itself the escape character, if a backslash appears in a
  /// filename, it should be escaped as well.  (As a special case, $ is escaped
  /// as $$, which is the normal Make way to handle the $ character.)
  /// For compatibility with BSD Make and historical practice, if GNU Make
  /// un-escapes characters in a filename but doesn't find a match, it will
  /// retry with the unmodified original string.
  ///
  /// GCC tries to accommodate both Make formats by escaping any space or #
  /// characters in the original filename, but not escaping backslashes.  The
  /// apparent intent is so that filenames with backslashes will be handled
  /// correctly by BSD Make, and by GNU Make in its fallback mode of using the
  /// unmodified original string; filenames with # or space characters aren't
  /// supported by BSD Make at all, but will be handled correctly by GNU Make
  /// due to the escaping.
  ///
  /// A corner case that GCC gets only partly right is when the original filename
  /// has a backslash immediately followed by space or #.  GNU Make would expect
  /// this backslash to be escaped; however GCC escapes the original backslash
  /// only when followed by space, not #.  It will therefore take a dependency
  /// from a directive such as
  ///     #include "a\ b\#c.h"
  /// and emit it as
  ///     a\\\ b\\#c.h
  /// which GNU Make will interpret as
  ///     a\ b\
  /// followed by a comment. Failing to find this file, it will fall back to the
  /// original string, which probably doesn't exist either; in any case it won't
  /// find
  ///     a\ b\#c.h
  /// which is the actual filename specified by the include directive.
  ///
  /// Clang does what GCC does, rather than what GNU Make expects.
  ///
  /// NMake/Jom has a different set of scary characters, but wraps filespecs in
  /// double-quotes to avoid misinterpreting them; see
  /// https://msdn.microsoft.com/en-us/library/dd9y37ha.aspx for NMake info,
  /// https://msdn.microsoft.com/en-us/library/windows/desktop/aa365247(v=vs.85).aspx
  /// for Windows file-naming info.
  static void PrintFilename(raw_ostream &OS, StringRef Filename,
                            DependencyOutputFormat OutputFormat) {
    // Convert filename to platform native path
    llvm::SmallString<256> NativePath;
    llvm::sys::path::native(Filename.str(), NativePath);
  
    if (OutputFormat == DependencyOutputFormat::NMake) {
      // Add quotes if needed. These are the characters listed as "special" to
      // NMake, that are legal in a Windows filespec, and that could cause
      // misinterpretation of the dependency string.
      if (NativePath.find_first_of(" #${}^!") != StringRef::npos)
        OS << '\"' << NativePath << '\"';
      else
        OS << NativePath;
      return;
    }
    assert(OutputFormat == DependencyOutputFormat::Make);
    for (unsigned i = 0, e = NativePath.size(); i != e; ++i) {
      if (NativePath[i] == '#') // Handle '#' the broken gcc way.
        OS << '\\';
      else if (NativePath[i] == ' ') { // Handle space correctly.
        OS << '\\';
        unsigned j = i;
        while (j > 0 && NativePath[--j] == '\\')
          OS << '\\';
      } else if (NativePath[i] == '$') // $ is escaped by $$.
        OS << '$';
      OS << NativePath[i];
    }
  }
  
  void DependencyFileGenerator::outputDependencyFile(DiagnosticsEngine &Diags) {
    if (SeenMissingHeader) {
      llvm::sys::fs::remove(OutputFile);
      return;
    }
  
    std::error_code EC;
    llvm::raw_fd_ostream OS(OutputFile, EC, llvm::sys::fs::OF_Text);
    if (EC) {
      Diags.Report(diag::err_fe_error_opening) << OutputFile << EC.message();
      return;
    }
  
    outputDependencyFile(OS);
  }
  
  void DependencyFileGenerator::outputDependencyFile(llvm::raw_ostream &OS) {
    // Write out the dependency targets, trying to avoid overly long
    // lines when possible. We try our best to emit exactly the same
    // dependency file as GCC (4.2), assuming the included files are the
    // same.
    const unsigned MaxColumns = 75;
    unsigned Columns = 0;
  
    for (StringRef Target : Targets) {
      unsigned N = Target.size();
      if (Columns == 0) {
        Columns += N;
      } else if (Columns + N + 2 > MaxColumns) {
        Columns = N + 2;
        OS << " \\\n  ";
      } else {
        Columns += N + 1;
        OS << ' ';
      }
      // Targets already quoted as needed.
      OS << Target;
    }
  
    OS << ':';
    Columns += 1;
  
    // Now add each dependency in the order it was seen, but avoiding
    // duplicates.
    ArrayRef<std::string> Files = getDependencies();
    for (StringRef File : Files) {
      // Start a new line if this would exceed the column limit. Make
      // sure to leave space for a trailing " \" in case we need to
      // break the line on the next iteration.
      unsigned N = File.size();
      if (Columns + (N + 1) + 2 > MaxColumns) {
        OS << " \\\n ";
        Columns = 2;
      }
      OS << ' ';
      PrintFilename(OS, File, OutputFormat);
      Columns += N + 1;
    }
    OS << '\n';
  
    // Create phony targets if requested.
    if (PhonyTarget && !Files.empty()) {
      unsigned Index = 0;
      for (auto I = Files.begin(), E = Files.end(); I != E; ++I) {
        if (Index++ == InputFileIndex)
          continue;
        OS << '\n';
        PrintFilename(OS, *I, OutputFormat);
        OS << ":\n";
      }
    }
  }
  