我正在使用 Clang 开发 AST 转换器。它应该将文件名作为输入，对该文件中的代码执行一些转换，然后返回转换后的代码。它基于 a helpful example from Eli Bendersky .

代码如下:

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());
}

这是我的输入程序，negate.cpp:

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

当我在此代码上运行 transform 时，出现以下错误:

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

这表明它在 C 模式下工作，而不是 C++ 模式。为了确认，我将 bool 替换为 int，将 true 替换为 1，将 false 替换为0:

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

这行得通，所以我的问题是:

如何将 Clang CompilerInstance 置于 C++ 模式？

更新:

我尝试更改调用，但没有成功:

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

  auto* compilerInvocation = new CompilerInvocation();

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

最佳答案

在执行编译器之前，您必须使用 getInvocation()/setInvocation() 方法检查/设置 CompilerInvocation 结构。该结构定义了语言选项(调用约定、垃圾回收……)、语言种类(C、CXX、Asm、ObjC……)、目标三元组、预处理器选项和语言标准。它是用 setLangDefaults() 方法设置的。

这是包含您要解析的语言的 InputKind 类。

如文档中所写，setLangDefaults() API

sets some properties which depend solely on the input kind

通过检查源代码，您可以看到以下构造函数调用层次结构:

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

在 LangOptions() 构造函数中，您可以看到没有设置特定/默认语言 ( LangOptions.def )。因此需要通过 setLangDefaults() 特定的 API。

你应该这样走:

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());
}

引用 clang 教程 CIRewriter.cpp ，这似乎也有点过时了。

关于c++ - 如何将 Clang 置于 C++ 模式？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/38356485/