如何使用clang仅获取main函数的AST

#include <iostream>
#include <clang/AST/ASTConsumer.h>
#include <clang/AST/RecursiveASTVisitor.h>
#include <clang/Frontend/ASTConsumers.h>
#include <clang/Frontend/CompilerInstance.h>
#include <clang/Tooling/CommonOptionsParser.h>
#include <clang/Tooling/Tooling.h>

using namespace clang;
using namespace clang::tooling;

class MainFunctionVisitor : public RecursiveASTVisitor<MainFunctionVisitor> {
public:
  bool VisitFunctionDecl(FunctionDecl *FD) {
    if (FD->getNameInfo().getName().getAsString() == "main") {
      FD->dump();
    }
    return true;
  }
};

class MainFunctionASTConsumer : public ASTConsumer {
public:
  void HandleTranslationUnit(ASTContext &Context) override {
    MainFunctionVisitor Visitor;
    Visitor.TraverseDecl(Context.getTranslationUnitDecl());
  }
};

int main(int argc, const char **argv) {
  CommonOptionsParser OptionsParser(argc, argv);
  ClangTool Tool(OptionsParser.getCompilations(),
                 OptionsParser.getSourcePathList());
  Tool.run(newFrontendActionFactory<MainFunctionASTConsumer>().get());
  return 0;
}

clang++ -std=c++11 -I <path_to_clang_headers> main_ast.cpp -o main_ast `llvm-config --cxxflags --ldflags --system-libs --libs core`

./main_ast <源代码文件>