//===--- 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/Support/FileSystem.h"

#include "llvm/Support/Path.h"

#include "llvm/Support/raw_ostream.h"

#include <optional>

using namespace clang;

namespace {

struct DepCollectorPPCallbacks : public PPCallbacks {

  DependencyCollector &DepCollector;

  Preprocessor &PP;

  DepCollectorPPCallbacks(DependencyCollector &L, Preprocessor &PP)

      : DepCollector(L), PP(PP) {}

  void LexedFileChanged(FileID FID, LexedFileChangeReason Reason,

                        SrcMgr::CharacteristicKind FileType, FileID PrevFID,

                        SourceLocation Loc) override {

    if (Reason != PPCallbacks::LexedFileChangeReason::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 (std::optional<StringRef> Filename =

            PP.getSourceManager().getNonBuiltinFilenameForID(FID))

      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,

                          OptionalFileEntryRef 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,

                  OptionalFileEntryRef 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(PP.getDiagnostics());

  }

};

struct DepCollectorMMCallbacks : public ModuleMapCallbacks {

  DependencyCollector &DepCollector;

  DepCollectorMMCallbacks(DependencyCollector &DC) : DepCollector(DC) {}

  void moduleMapFileRead(SourceLocation Loc, FileEntryRef Entry,

                         bool IsSystem) override {

    StringRef Filename = Entry.getName();

    DepCollector.maybeAddDependency(Filename, /*FromModule*/ false,

                                    /*IsSystem*/ IsSystem,

                                    /*IsModuleFile*/ false,

                                    /*IsMissing*/ false);

  }

};

struct DepCollectorASTListener : public ASTReaderListener {

  DependencyCollector &DepCollector;

  FileManager &FileMgr;

  DepCollectorASTListener(DependencyCollector &L, FileManager &FileMgr)

      : DepCollector(L), FileMgr(FileMgr) {}

  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;

    // Run this through the FileManager in order to respect 'use-external-name'

    // in case we have a VFS overlay.

    if (auto FE = FileMgr.getOptionalFileRef(Filename))

      Filename = FE->getName();

    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) {

  StringRef SearchPath;

#ifdef _WIN32

  // Make the search insensitive to case and separators.

  llvm::SmallString<256> TmpPath = Filename;

  llvm::sys::path::native(TmpPath);

  std::transform(TmpPath.begin(), TmpPath.end(), TmpPath.begin(), ::tolower);

  SearchPath = TmpPath.str();

#else

  SearchPath = Filename;

#endif

  if (Seen.insert(SearchPath).second) {

    Dependencies.push_back(std::string(Filename));

    return true;

  }

  return false;

}

static bool isSpecialFilename(StringRef Filename) {

  return Filename == "<built-in>";

}

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));

  PP.getHeaderSearchInfo().getModuleMap().addModuleMapCallbacks(

      std::make_unique<DepCollectorMMCallbacks>(*this));

}

void DependencyCollector::attachToASTReader(ASTReader &R) {

  R.addListener(

      std::make_unique<DepCollectorASTListener>(*this, R.getFileManager()));

}

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),

      OutputFormat(Opts.OutputFormat), InputFileIndex(0) {

  for (const auto &ExtraDep : Opts.ExtraDeps) {

    if (addDependency(ExtraDep.first))

      ++InputFileIndex;

  }

}

void DependencyFileGenerator::attachToPreprocessor(Preprocessor &PP) {

  // Disable the "file not found" diagnostic if the -MG option was given.

  if (AddMissingHeaderDeps)

    PP.SetSuppressIncludeNotFoundError(true);

  DependencyCollector::attachToPreprocessor(PP);

}

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_TextWithCRLF);

  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>=10, 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) {

    if (File == "<stdin>")

      continue;

    // 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;

      PrintFilename(OS, *I, OutputFormat);

      OS << ":\n";

    }

  }

}