[boost] [asio] how to handle "boost::asio::placeholders::error" in "boost::function"?

Hi all, I met a problem which can't be solved. Can any kind people help me? The code looks like the below: class transfor_data { public: void one_fun( const boost::system::error_code& e, connection conn ) { ... } void another_fun() { { //compile error because of the placeholder boost::function<void(void)> fun = boost::bind(&transfor_file_push::write_file, this, boost::asio::placeholders::error, conn); } { //fine without placeholder boost::system::error_code e; boost::function<void(void)> fun = boost::bind(&transfor_file_push::write_file, this, e, conn); } } }