//===-- HeaderIncludeGen.cpp - Generate Header Includes -------------------===//

//

// 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/DependencyOutputOptions.h"

#include "clang/Frontend/Utils.h"

#include "clang/Basic/SourceManager.h"

#include "clang/Frontend/FrontendDiagnostic.h"

#include "clang/Lex/Preprocessor.h"

#include "llvm/ADT/SmallString.h"

#include "llvm/Support/JSON.h"

#include "llvm/Support/raw_ostream.h"

using namespace clang;

namespace {

class HeaderIncludesCallback : public PPCallbacks {

  SourceManager &SM;

  raw_ostream *OutputFile;

  const DependencyOutputOptions &DepOpts;

  unsigned CurrentIncludeDepth;

  bool HasProcessedPredefines;

  bool OwnsOutputFile;

  bool ShowAllHeaders;

  bool ShowDepth;

  bool MSStyle;

public:

  HeaderIncludesCallback(const Preprocessor *PP, bool ShowAllHeaders_,

                         raw_ostream *OutputFile_,

                         const DependencyOutputOptions &DepOpts,

                         bool OwnsOutputFile_, bool ShowDepth_, bool MSStyle_)

      : SM(PP->getSourceManager()), OutputFile(OutputFile_), DepOpts(DepOpts),

        CurrentIncludeDepth(0), HasProcessedPredefines(false),

        OwnsOutputFile(OwnsOutputFile_), ShowAllHeaders(ShowAllHeaders_),

        ShowDepth(ShowDepth_), MSStyle(MSStyle_) {}

  ~HeaderIncludesCallback() override {

    if (OwnsOutputFile)

      delete OutputFile;

  }

  HeaderIncludesCallback(const HeaderIncludesCallback &) = delete;

  HeaderIncludesCallback &operator=(const HeaderIncludesCallback &) = delete;

  void FileChanged(SourceLocation Loc, FileChangeReason Reason,

                   SrcMgr::CharacteristicKind FileType,

                   FileID PrevFID) override;

  void FileSkipped(const FileEntryRef &SkippedFile, const Token &FilenameTok,

                   SrcMgr::CharacteristicKind FileType) override;

private:

  bool ShouldShowHeader(SrcMgr::CharacteristicKind HeaderType) {

    if (!DepOpts.IncludeSystemHeaders && isSystem(HeaderType))

      return false;

    // Show the current header if we are (a) past the predefines, or (b) showing

    // all headers and in the predefines at a depth past the initial file and

    // command line buffers.

    return (HasProcessedPredefines ||

            (ShowAllHeaders && CurrentIncludeDepth > 2));

  }

};

/// A callback for emitting header usage information to a file in JSON. Each

/// line in the file is a JSON object that includes the source file name and

/// the list of headers directly or indirectly included from it. For example:

///

/// {"source":"/tmp/foo.c",

///  "includes":["/usr/include/stdio.h", "/usr/include/stdlib.h"]}

///

/// To reduce the amount of data written to the file, we only record system

/// headers that are directly included from a file that isn't in the system

/// directory.

class HeaderIncludesJSONCallback : public PPCallbacks {

  SourceManager &SM;

  raw_ostream *OutputFile;

  bool OwnsOutputFile;

  SmallVector<std::string, 16> IncludedHeaders;

public:

  HeaderIncludesJSONCallback(const Preprocessor *PP, raw_ostream *OutputFile_,

                             bool OwnsOutputFile_)

      : SM(PP->getSourceManager()), OutputFile(OutputFile_),

        OwnsOutputFile(OwnsOutputFile_) {}

  ~HeaderIncludesJSONCallback() override {

    if (OwnsOutputFile)

      delete OutputFile;

  }

  HeaderIncludesJSONCallback(const HeaderIncludesJSONCallback &) = delete;

  HeaderIncludesJSONCallback &

  operator=(const HeaderIncludesJSONCallback &) = delete;

  void EndOfMainFile() override;

  void FileChanged(SourceLocation Loc, FileChangeReason Reason,

                   SrcMgr::CharacteristicKind FileType,

                   FileID PrevFID) override;

  void FileSkipped(const FileEntryRef &SkippedFile, const Token &FilenameTok,

                   SrcMgr::CharacteristicKind FileType) override;

};

}

static void PrintHeaderInfo(raw_ostream *OutputFile, StringRef Filename,

                            bool ShowDepth, unsigned CurrentIncludeDepth,

                            bool MSStyle) {

  // Write to a temporary string to avoid unnecessary flushing on errs().

  SmallString<512> Pathname(Filename);

  if (!MSStyle)

    Lexer::Stringify(Pathname);

  SmallString<256> Msg;

  if (MSStyle)

    Msg += "Note: including file:";

  if (ShowDepth) {

    // The main source file is at depth 1, so skip one dot.

    for (unsigned i = 1; i != CurrentIncludeDepth; ++i)

      Msg += MSStyle ? ' ' : '.';

    if (!MSStyle)

      Msg += ' ';

  }

  Msg += Pathname;

  Msg += '\n';

  *OutputFile << Msg;

  OutputFile->flush();

}

void clang::AttachHeaderIncludeGen(Preprocessor &PP,

                                   const DependencyOutputOptions &DepOpts,

                                   bool ShowAllHeaders, StringRef OutputPath,

                                   bool ShowDepth, bool MSStyle) {

  raw_ostream *OutputFile = &llvm::errs();

  bool OwnsOutputFile = false;

  // Choose output stream, when printing in cl.exe /showIncludes style.

  if (MSStyle) {

    switch (DepOpts.ShowIncludesDest) {

    default:

      llvm_unreachable("Invalid destination for /showIncludes output!");

    case ShowIncludesDestination::Stderr:

      OutputFile = &llvm::errs();

      break;

    case ShowIncludesDestination::Stdout:

      OutputFile = &llvm::outs();

      break;

    }

  }

  // Open the output file, if used.

  if (!OutputPath.empty()) {

    std::error_code EC;

    llvm::raw_fd_ostream *OS = new llvm::raw_fd_ostream(

        OutputPath.str(), EC,

        llvm::sys::fs::OF_Append | llvm::sys::fs::OF_TextWithCRLF);

    if (EC) {

      PP.getDiagnostics().Report(clang::diag::warn_fe_cc_print_header_failure)

          << EC.message();

      delete OS;

    } else {

      OS->SetUnbuffered();

      OutputFile = OS;

      OwnsOutputFile = true;

    }

  }

  switch (DepOpts.HeaderIncludeFormat) {

  case HIFMT_None:

    llvm_unreachable("unexpected header format kind");

  case HIFMT_Textual: {

    assert(DepOpts.HeaderIncludeFiltering == HIFIL_None &&

           "header filtering is currently always disabled when output format is"

           "textual");

    // Print header info for extra headers, pretending they were discovered by

    // the regular preprocessor. The primary use case is to support proper

    // generation of Make / Ninja file dependencies for implicit includes, such

    // as sanitizer ignorelists. It's only important for cl.exe compatibility,

    // the GNU way to generate rules is -M / -MM / -MD / -MMD.

    for (const auto &Header : DepOpts.ExtraDeps)

      PrintHeaderInfo(OutputFile, Header.first, ShowDepth, 2, MSStyle);

    PP.addPPCallbacks(std::make_unique<HeaderIncludesCallback>(

        &PP, ShowAllHeaders, OutputFile, DepOpts, OwnsOutputFile, ShowDepth,

        MSStyle));

    break;

  }

  case HIFMT_JSON: {

    assert(DepOpts.HeaderIncludeFiltering == HIFIL_Only_Direct_System &&

           "only-direct-system is the only option for filtering");

    PP.addPPCallbacks(std::make_unique<HeaderIncludesJSONCallback>(

        &PP, OutputFile, OwnsOutputFile));

    break;

  }

  }

}

void HeaderIncludesCallback::FileChanged(SourceLocation Loc,

                                         FileChangeReason Reason,

                                         SrcMgr::CharacteristicKind NewFileType,

                                         FileID PrevFID) {

  // Unless we are exiting a #include, make sure to skip ahead to the line the

  // #include directive was at.

  PresumedLoc UserLoc = SM.getPresumedLoc(Loc);

  if (UserLoc.isInvalid())

    return;

  // Adjust the current include depth.

  if (Reason == PPCallbacks::EnterFile) {

    ++CurrentIncludeDepth;

  } else if (Reason == PPCallbacks::ExitFile) {

    if (CurrentIncludeDepth)

      --CurrentIncludeDepth;

    // We track when we are done with the predefines by watching for the first

    // place where we drop back to a nesting depth of 1.

    if (CurrentIncludeDepth == 1 && !HasProcessedPredefines)

      HasProcessedPredefines = true;

    return;

  } else {

    return;

  }

  if (!ShouldShowHeader(NewFileType))

    return;

  unsigned IncludeDepth = CurrentIncludeDepth;

  if (!HasProcessedPredefines)

    --IncludeDepth; // Ignore indent from <built-in>.

  // FIXME: Identify headers in a more robust way than comparing their name to

  // "<command line>" and "<built-in>" in a bunch of places.

  if (Reason == PPCallbacks::EnterFile &&

      UserLoc.getFilename() != StringRef("<command line>")) {

    PrintHeaderInfo(OutputFile, UserLoc.getFilename(), ShowDepth, IncludeDepth,

                    MSStyle);

  }

}

void HeaderIncludesCallback::FileSkipped(const FileEntryRef &SkippedFile, const

                                         Token &FilenameTok,

                                         SrcMgr::CharacteristicKind FileType) {

  if (!DepOpts.ShowSkippedHeaderIncludes)

    return;

  if (!ShouldShowHeader(FileType))

    return;

  PrintHeaderInfo(OutputFile, SkippedFile.getName(), ShowDepth,

                  CurrentIncludeDepth + 1, MSStyle);

}

void HeaderIncludesJSONCallback::EndOfMainFile() {

  OptionalFileEntryRef FE = SM.getFileEntryRefForID(SM.getMainFileID());

  SmallString<256> MainFile(FE->getName());

  SM.getFileManager().makeAbsolutePath(MainFile);

  std::string Str;

  llvm::raw_string_ostream OS(Str);

  llvm::json::OStream JOS(OS);

  JOS.object([&] {

    JOS.attribute("source", MainFile.c_str());

    JOS.attributeArray("includes", [&] {

      llvm::StringSet<> SeenHeaders;

      for (const std::string &H : IncludedHeaders)

        if (SeenHeaders.insert(H).second)

          JOS.value(H);

    });

  });

  OS << "\n";

  if (OutputFile->get_kind() == raw_ostream::OStreamKind::OK_FDStream) {

    llvm::raw_fd_ostream *FDS = static_cast<llvm::raw_fd_ostream *>(OutputFile);

    if (auto L = FDS->lock())

      *OutputFile << Str;

  } else

    *OutputFile << Str;

}

/// Determine whether the header file should be recorded. The header file should

/// be recorded only if the header file is a system header and the current file

/// isn't a system header.

static bool shouldRecordNewFile(SrcMgr::CharacteristicKind NewFileType,

                                SourceLocation PrevLoc, SourceManager &SM) {

  return SrcMgr::isSystem(NewFileType) && !SM.isInSystemHeader(PrevLoc);

}

void HeaderIncludesJSONCallback::FileChanged(

    SourceLocation Loc, FileChangeReason Reason,

    SrcMgr::CharacteristicKind NewFileType, FileID PrevFID) {

  if (PrevFID.isInvalid() ||

      !shouldRecordNewFile(NewFileType, SM.getLocForStartOfFile(PrevFID), SM))

    return;

  // Unless we are exiting a #include, make sure to skip ahead to the line the

  // #include directive was at.

  PresumedLoc UserLoc = SM.getPresumedLoc(Loc);

  if (UserLoc.isInvalid())

    return;

  if (Reason == PPCallbacks::EnterFile &&

      UserLoc.getFilename() != StringRef("<command line>"))

    IncludedHeaders.push_back(UserLoc.getFilename());

}

void HeaderIncludesJSONCallback::FileSkipped(

    const FileEntryRef &SkippedFile, const Token &FilenameTok,

    SrcMgr::CharacteristicKind FileType) {

  if (!shouldRecordNewFile(FileType, FilenameTok.getLocation(), SM))

    return;

  IncludedHeaders.push_back(SkippedFile.getName().str());

}