如何將Clang置於C ++模式？

Question

我正在使用Clang開發AST變壓器。 它應該將文件名作為輸入，對該文件中的代碼執行一些轉換，並返回轉換后的代碼。 它基於Eli Bendersky的一個有用的例子 。

這是代碼：

std::string transform(std::string fileName) {

  // CompilerInstance will hold the instance of the Clang compiler for us,
  // managing the various objects needed to run the compiler.
  CompilerInstance compilerInstance;

  compilerInstance.createDiagnostics();

  auto& langOpts = compilerInstance.getLangOpts();
  langOpts.CPlusPlus = true;

  // Initialize target info with the default triple for our platform.
  auto TO = std::make_shared<TargetOptions>();
  TO->Triple = llvm::sys::getDefaultTargetTriple();
  TargetInfo* targetInfo =
      TargetInfo::CreateTargetInfo(compilerInstance.getDiagnostics(), TO);
  compilerInstance.setTarget(targetInfo);

  compilerInstance.createFileManager();
  auto& fileManager = compilerInstance.getFileManager();

  compilerInstance.createSourceManager(fileManager);
  auto& sourceManager = compilerInstance.getSourceManager();

  compilerInstance.createPreprocessor(TU_Module);
  compilerInstance.createASTContext();

  // A Rewriter helps us manage the code rewriting task.
  auto rewriter = clang::Rewriter(sourceManager, compilerInstance.getLangOpts());

  // Set the main file handled by the source manager to the input file.
  const FileEntry* inputFile = fileManager.getFile(fileName);
  sourceManager.setMainFileID(
      sourceManager.createFileID(inputFile, SourceLocation(), SrcMgr::C_User));
  compilerInstance.getDiagnosticClient().BeginSourceFile(
      compilerInstance.getLangOpts(), &compilerInstance.getPreprocessor());

  // Create an AST consumer instance which is going to get called by
  // ParseAST.
  MyASTConsumer consumer(rewriter);

  // Parse the file to AST, registering our consumer as the AST consumer.
  clang::ParseAST(
    compilerInstance.getPreprocessor(), 
    &consumer, 
    compilerInstance.getASTContext());

  // At this point the rewriter's buffer should be full with the rewritten
  // file contents.
  const RewriteBuffer* buffer = rewriter.getRewriteBufferFor(sourceManager.getMainFileID());

  return std::string(buffer->begin(), buffer->end());
}

這是我的輸入程序， negate.cpp ：

bool negate(bool b) {
    if (b) {
        return false;
    } else {
        return true;
    }
}

當我對此代碼運行transform ，我收到以下錯誤：

negate.cpp:1:1: error: unknown type name 'bool'
bool negate(bool b) {
^

這告訴我它在C模式下工作，而不是C ++模式。 為了確認，我用int替換bool ，用1替換true ，用0替換false ：

int negate(int b) {
    if (b) {
        return 0;
    } else {
        return 1;
    }
}

這很有用，所以我的問題是：

如何將Clang CompilerInstance放入C ++模式？

---

更新：

我試着改變調用，但沒有運氣：

  auto& langOpts = compilerInstance.getLangOpts();
  langOpts.CPlusPlus = true;
  langOpts.CPlusPlus11 = true;

  auto* compilerInvocation = new CompilerInvocation();

  compilerInvocation->setLangDefaults(
    langOpts, 
    clang::InputKind::IK_CXX, 
    LangStandard::lang_gnu11);

Answer 1

在執行編譯器之前，必須使用getInvocation() / setInvocation()方法檢查/設置CompilerInvocation結構。 此結構定義語言選項（調用約定，垃圾收集，...），語言類型（C，CXX，Asm，ObjC，...），目標三元組，預處理器選項和語言標准。 它使用setLangDefaults()方法設置。

這是InputKind類，它包含您要解析的語言。

如文檔中所述， setLangDefaults() API

設置一些僅依賴於輸入類型的屬性

通過檢查源代碼，您可以看到以下構造函數調用層次結構：

• CompilerInstance()
• CompilerInvocation()
• CompilerInvocationBase()
• LangOptions()

在LangOptions()構造函數中，您可以看到沒有設置特定/默認語言（ LangOptions.def ）。 因此需要通過setLangDefaults（）特定的API。

你應該這樣：

std::string transform(std::string fileName) {

  CompilerInstance compilerInstance;
  compilerInstance.createDiagnostics();

  CompilerInvocation & invocation = compilerInstance.getInvocation();

  // Initialize target info with the default triple for our platform.
  auto TO = std::make_shared<TargetOptions>();
  TO->Triple = llvm::sys::getDefaultTargetTriple();
  TargetInfo* targetInfo =
      TargetInfo::CreateTargetInfo(compilerInstance.getDiagnostics(), TO);
  compilerInstance.setTarget(targetInfo);

  compilerInstance.createFileManager();
  auto& fileManager = compilerInstance.getFileManager();

  compilerInstance.createSourceManager(fileManager);
  auto& sourceManager = compilerInstance.getSourceManager();

  LangOptions langOpts; 
  langOpts.GNUMode = 1;  
  langOpts.CXXExceptions = 1;  
  langOpts.RTTI = 1;  
  langOpts.Bool = 1;   // <-- Note the Bool option here !
  langOpts.CPlusPlus = 1;  
  PreprocessorOptions &PPOpts = compilerInstance.getPreprocessorOpts();

  invocation.setLangDefaults(langOpts, 
                             clang::IK_CXX,
                             TO->Triple, 
                             PPOpts,
                             clang::LangStandard::lang_cxx0x); 


  compilerInstance.createPreprocessor(TU_Module);
  compilerInstance.createASTContext();

  // A Rewriter helps us manage the code rewriting task.
  auto rewriter = clang::Rewriter(sourceManager, compilerInstance.getLangOpts());

  // Set the main file handled by the source manager to the input file.
  const FileEntry* inputFile = fileManager.getFile(fileName);
  sourceManager.setMainFileID(
      sourceManager.createFileID(inputFile, SourceLocation(), SrcMgr::C_User));
  compilerInstance.getDiagnosticClient().BeginSourceFile(
      compilerInstance.getLangOpts(), &compilerInstance.getPreprocessor());

  // Create an AST consumer instance which is going to get called by
  // ParseAST.
  MyASTConsumer consumer(rewriter);

  // Parse the file to AST, registering our consumer as the AST consumer.
  clang::ParseAST(
    compilerInstance.getPreprocessor(), 
    &consumer, 
    compilerInstance.getASTContext());

  // At this point the rewriter's buffer should be full with the rewritten
  // file contents.
  const RewriteBuffer* buffer = rewriter.getRewriteBufferFor(sourceManager.getMainFileID());

  return std::string(buffer->begin(), buffer->end());
}

在clang教程CIRewriter.cpp中引用 ，這似乎也有點過時了。