passing functor to std::thread with ctor parameters. is it possible?

3
votes
class worker {
    std::atomic_bool done;
    std::string segment_name;
    bi::named_mutex mutex;
    std::string file_name;
    data_segment_state state;
    unsigned long data_size;
    std::unique_ptr<unsigned char> data;
protected:
    void operator()() {
        while(!done) {
        }
    }

public:
    worker(const std::string& _segment_name, bi::managed_shared_memory& segment)
    : done{false},
          segment_name{_segment_name},
          mutex{bi::open_or_create, segment_name.c_str() },
          file_name {},
          state {data_segment_state::not_received },
          data_size{0},
          data {segment.construct<unsigned char>(segment_name.c_str())[chunk_size](0) } 
    }

    worker(worker&& rhs)
    : done {rhs.done.load()} ,
      mutex(bi::open_or_create, rhs.segment_name.c_str()),
      segment_name{rhs.segment_name},
      file_name {rhs.file_name},
      state {rhs.state },
      data_size{rhs.data_size},
      data {std::move(rhs.data)} {
    }
};

...

 std::string worker_name;
        std::thread t{worker{worker_name, segment}};

In instantiation of 'struct std::_Bind_simple<worker()>':
thread:137:47:   required from 'std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = worker; _Args = {}]'
error: no type named 'type' in 'class std::result_of<worker()>'
       typedef typename result_of<_Callable(_Args...)>::type result_type;

what is a valid thread initialization with functional object? full text of error: error: no type named 'type' in 'class
std::result_of' typedef typename result_of<_Callable(_Args...)>::type result_type; ^

2
c++multithreading
create a worker then pass it to the thread constructor. - RamblingMad
"does also produces the same error with a using default ctor" No it doesn't. I guess you are not showing us the code that you are compiling, and you're actually getting some other error that we can't possibly guess. - Jonathan Wakely
let me update the question with a code as full as I can, and output of GCC from console - amigo421
You should really have done that before asking a question. See stackoverflow.com/help/mcve - Jonathan Wakely

2 Answers

3
votes

Just pass the constructed functor:

std::thread t(worker{str, 10});

Live demo

The constructor of std::thread you are referring to takes a constructed function object and arguments that will be passed when calling that function object. So in your case the arguments would be passed to operator().

2
votes

The issue was in the my inattention: operator() was in protected section . moving to public solves the problem