Re: [Boost-users] Can I return std::unique_ptr in a boost::future?

Subject: Re: [Boost-users] Can I return std::unique_ptr in a boost::future?
From: Vicente J. Botet Escriba (vicente.botet_at_[hidden])
Date: 2013-11-15 14:38:33

Le 15/11/13 17:14, Aaron_Wright_at_[hidden] a écrit :
> Is this code expected to work then? I just need to upgrade my boost? I'm
> currently using 1.49. I just want to make sure before I go through the
> work of upgrading boost.

No, Boost.Thread with BOOST_THREAD_VERSION = 2 which is the default 
doesn't provides C++11 move semantics. You need to add

#define BOOST_THREAD_VERSION 4

or

#define BOOST_THREAD_VERSION 3

before including ant Boost file and change unique_future by future.

I suspect that you need at least boost.1.50.

Version 3.0.0 - boost 1.50

Breaking changes when BOOST_THREAD_VERSION==3:

     #6229 Breaking change: Rename the unique_future to future following 
the c++11.
     #6266 Breaking change: thread destructor should call terminate if 
joinable.
     #6269 Breaking change: thread move assignment should call terminate 
if joinable.

New Features:

     #6194 Adapt to Boost.Move.

I expect that helps,
Vicente
>
> ---
>
> Aaron Wright
>
>
>
> From:   "Vicente J. Botet Escriba" <vicente.botet_at_[hidden]>
> To:     boost-users_at_[hidden]
> Date:   11/14/2013 11:28 PM
> Subject:        Re: [Boost-users] Can I return std::unique_ptr in a
> boost::future?
> Sent by:        "Boost-users" <boost-users-bounces_at_[hidden]>
>
>
>
> Le 15/11/13 02:05, Aaron_Wright_at_[hidden] a écrit :
>> I'm trying to return a std::unique_ptr in a boost::future. I can't get
> it
>> to compile. Is it possible? The code wraps a packaged_task in a functor
> to
>> make it copyable enough to pass to a boost::asio::io_service, where the
>> work will be done in another thread. The code works for other return
> types
>> that are copyable.
>>
>> This is what I have for a small test case:
>>
>> std::unique_ptr< int > get_int_impl(int i)
>> {
>>      return std::unique_ptr< int >(new int(i));
>> }
>>
>> std::unique_ptr< int > get_int(int i)
>> {
>>      typedef boost::packaged_task< std::unique_ptr< int > > Task;
>>
>>      boost::shared_ptr< Task > task = boost::make_shared< Task
>>> (boost::bind(&get_int_impl, 42));
>>      boost::unique_future< std::unique_ptr< int > > future =
>> task->get_future(); // <--- Error from this line.
>>
>>      m_service.post(boost::bind(&Task::operator(), task));
>>
>>      return future.get();
>> }
>>
>> BOOST_AUTO_TEST_CASE(test_get_int)
>> {
>>      BOOST_CHECK_EQUAL(*get_int(42), 42);
>> }
>>
>> The error:
>>
>> boost/thread/future.hpp(239): error C2248:
>> 'std::unique_ptr<_Ty>::unique_ptr' : cannot access private member
> declared
>> in class 'std::unique_ptr<_Ty>'
>> ---
>>
>>
> Hi, please try defining BOOST_VERSION 4 and using boost::future instead
> and let me know.
>
> Best,
> Vicente
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