[ 33%] Building CXX object CMakeFiles/http_server.dir/EchoServer.cpp.o
[ 66%] Building CXX object CMakeFiles/http_server.dir/EchoHandler.cpp.o
[100%] Linking CXX executable http_server
Undefined symbols for architecture x86_64:
  "proxygen::HTTPServer::bind(std::__1::vector<proxygen::HTTPServer::IPConfig, std::__1::allocator<proxygen::HTTPServer::IPConfig>> const&)", referenced from:
      _main in EchoServer.cpp.o
  "proxygen::HTTPServer::start(std::__1::function<void ()>, std::__1::function<void (std::exception_ptr)>, std::__1::function<std::__1::shared_ptr<wangle::AcceptorFactory> (proxygen::HTTPServer::AcceptorFactoryConfig)>, std::__1::shared_ptr<folly::IOThreadPoolExecutorBase>)", referenced from:
      main::$_0::operator()() const in EchoServer.cpp.o
  "proxygen::HTTPServer::HTTPServer(proxygen::HTTPServerOptions)", referenced from:
      _main in EchoServer.cpp.o
  "proxygen::HTTPServer::~HTTPServer()", referenced from:
      _main in EchoServer.cpp.o
  "___cxa_decrement_exception_refcount", referenced from:
      folly::detail::exception_cleanup_(_Unwind_Reason_Code, _Unwind_Exception*) in libfolly.a(Exception.cpp.o)
  "___cxa_increment_exception_refcount", referenced from:
      folly::detail::exception_ptr_get_type_(std::exception_ptr const&) in libfolly.a(Exception.cpp.o)
      folly::detail::exception_ptr_get_object_(std::exception_ptr const&, std::type_info const*) in libfolly.a(Exception.cpp.o)
      folly::detail::make_exception_ptr_with_(folly::detail::make_exception_ptr_with_arg_ const&, void*) in libfolly.a(Exception.cpp.o)
      decltype(auto) folly::detail::cxxabi_with_cxa_exception<folly::detail::exception_cleanup_(_Unwind_Reason_Code, _Unwind_Exception*)::$_1>(void*, folly::detail::exception_cleanup_(_Unwind_Reason_Code, _Unwind_Exception*)::$_1) in libfolly.a(Exception.cpp.o)
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [http_server] Error 1
make[1]: *** [CMakeFiles/http_server.dir/all] Error 2
make: *** [all] Error 2