Re: [Boost-users] problems with Boost.Thread on VS10

Subject: Re: [Boost-users] problems with Boost.Thread on VS10
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2012-04-06 12:59:00

Le 06/04/12 08:04, John M. Dlugosz a écrit :
> On 4/5/2012 2:32 AM, Igor R wrote:
>> Can you provide a trivial example that reproduces the issue?
>>
>

See below some points that don't work yet with Boost.
>
>
> #include "boost/test/unit_test.hpp"
> #include "boost/thread/future.hpp"
> #include "boost/utility/result_of.hpp"
> #include <functional>
>
> struct async_func {
>     virtual ~async_func() { }
>     virtual void run() =0;
>     };
>
> template <typename Ret>
> class async_func_pt : public async_func {
>     boost::packaged_task<Ret> f;
> public:
>     void run() override { f(); }
>     async_func_pt (boost::packaged_task<Ret>&& f) : f(std::move(f)) {}
Should't you use std::forward here?
>     ~async_func_pt() { }
>     boost::unique_future<Ret> get_future()  { return f.get_future(); }
>     };
>
> void async_core (async_func* p);
>
>
>
>
> template <typename F>
> boost::unique_future<typename boost::result_of< F() >::type>
> async (F&& f)
>  {
>  typedef typename boost::result_of< F() >::type RetType;
>  async_func_pt<RetType>* p= new  async_func_pt<RetType> 
> (boost::packaged_task<RetType>(f));
>  boost::unique_future<RetType> future_result= p->get_future();
>  async_core (p);
>  return std::move(future_result);
>  }
>
> template <typename F, typename A1>
> boost::unique_future<typename boost::result_of< F(A1) >::type>
> async (F&& f, A1&& a1)
>  {
> // This should be all it needs.  But get a funny error deep inside Boost.
> // problem overloading with && ?
>  return async (std::tr1::bind(f,a1));
>  }
>
I don't think std::tr1::bind manage with rvalue references. Is this the 
Boost version?
Have you tried using std::bind?
> BOOST_AUTO_TEST_SUITE(thread_pool_tests)
>
> int calculate_the_answer_to_life_the_universe_and_everything()
> {
>     return 42;
> }
>
>
> size_t foo (const std::string& s)
>  {
>  return s.size();
>  }
>
>
>
> BOOST_AUTO_TEST_CASE( async_test )
> {
> // this one works
>     // most fundimental form:
>     boost::unique_future<int> fi= async 
> (&calculate_the_answer_to_life_the_universe_and_everything);
>     int i= fi.get();
>     BOOST_CHECK_EQUAL (i, 42);
>
>
> // This one chokes at compile time
>     boost::unique_future<size_t> fut_1= async (&foo, "Life");
>
>     BOOST_CHECK_EQUAL (fut_1.get(), 4);
> }
>
>
> BOOST_AUTO_TEST_SUITE_END()
>
>
As you are using std::move, &&, ... why not using directly the C++11 
Thread library provided with the compiler?

BTW, Boost.Thread could not implement async using Boost, as Boost.Tuple, 
Boost.Bind Boost.Fusion (Tuple) because these libraries dont manage with 
rvalue references.

Best,
Vicente