https://svn.boost.org/trac10/ticket/9303 <p> Setup consists of client(s), a server, and device(s). </p> <p> A client interacts with a device by sending requests to the server. These requests are examined and routed to the appropriate device. Requests are handled asynchronously, and are occasionally queued up via boost::asio::io_service::strand for various reasons. </p> <p> It appears as if packaged_task has a few different templates to choose from: </p> <p> packaged_task&lt;R&gt; packaged_task&lt;R()&gt; packaged_task&lt;R(<a class="missing wiki">ArgTypes</a>)&gt; </p> <p> To ensure that I was using the function correctly, I started simple; using the simple example on the boost::futures page as a starting point. From there, I created four simple functions: </p> <p> int return, no parameters. int return, with parameters. std::string return, no parameters. std::string return, with parameters. Test functions </p> <pre class="wiki">std::string ans("forty two"); int int_no_params() { return 42; } int int_with_params(int param) { return param; } std::string string_no_params() { return std::string("forty two"); } std::string string_with_params(std::string &amp; param) // Have tried both with and without '&amp;' { return param; } </pre><p> EXAMPLE 1: </p> <pre class="wiki">int function(void) //! Compiles and produces correct result. { boost::packaged_task&lt;int()&gt; example(int_no_params); boost::future&lt;int&gt; f = example.get_future(); boost::thread task(boost::move(example)); int answer = f.get(); std::cout &lt;&lt; "Answer to life and whatnot, in English: " &lt;&lt; answer &lt;&lt; std::endl; task.join(); } </pre><p> EXAMPLE 2: </p> <pre class="wiki"> std::string function(void) //! Compiles and produces correct result. { boost::packaged_task&lt;std::string()&gt; example(string_no_params); boost::future&lt;std::string&gt; f = example.get_future(); boost::thread task(boost::move(example)); std::string answer = f.get(); std::cout &lt;&lt; "string_no_params: " &lt;&lt; answer &lt;&lt; std::endl; task.join(); } </pre><p> EXAMPLE 3: </p> <pre class="wiki"> std::string(std::string&amp; param) No threading //! Doesn't compile. //! error: variable ‘boost::packaged_task&lt;std::basic_string&lt;char&gt;(std::basic_string&lt;char&gt;&amp;)&gt; example’ has initializer but incomplete type { boost::packaged_task&lt;std::string(std::string&amp;)&gt; example(string_with_params); boost::future&lt;std::string&gt; f = example.get_future(); example(ans); std::string answer = f.get(); std::cout &lt;&lt; "string_with_params: " &lt;&lt; answer &lt;&lt; std::endl; } </pre><p> EXAMPLE 4: </p> <pre class="wiki"> using boost::threading //! Doesn't compile. //! error: variable ‘boost::packaged_task&lt;std::basic_string&lt;char&gt;(std::basic_string&lt;char&gt;&amp;)&gt; example’ has initializer but incomplete type { boost::packaged_task&lt;std::string(std::string&amp;)&gt; example(string_with_params); boost::future&lt;std::string&gt; f = example.get_future(); boost::thread task(boost::move(example), ans); std::string answer = f.get(); std::cout &lt;&lt; "string_with_params: " &lt;&lt; answer &lt;&lt; std::endl; task.join(); } </pre><p> EXAMPLE 5: </p> <pre class="wiki">//Using extended initializers in packaged_task declaration //! Doesn't compile in C++03, C++11 only. //! error: extended initializer lists only available with -std=c++11 or -std=gnu++11 [-Werror] { boost::packaged_task&lt;std::string(std::string&amp;)&gt; example { boost::bind(&amp;string_with_params, ans) }; boost::future&lt;std::string&gt; f = example.get_future(); boost::thread task(boost::move(example), ans); std::string answer = f.get(); std::cout &lt;&lt; "string_with_params: " &lt;&lt; answer &lt;&lt; std::endl; task.join(); } </pre><p> EXAMPLE 6: </p> <pre class="wiki">//Threaded, using shared_ptr //The following use typedef boost::packaged_task&lt;std::string(std::string&amp;)&gt; task_t; //Because packaged tasks can't be copied, binding //shared_ptr&lt;T&gt;::operator() to task was a suggested solution found on stackoverflow. // error: invalid use of incomplete type ‘class boost::packaged_task&lt;std::basic_string&lt;char&gt;(std::basic_string&lt;char&gt;&amp;)&gt;’ // error: incomplete type ‘task_t {aka boost::packaged_task&lt;std::basic_string&lt;char&gt;(std::basic_string&lt;char&gt;&amp;)&gt;}’ used in nested name specifier // boost/thread/future.hpp:1320:11: error: declaration of ‘class boost::packaged_task&lt;std::basic_string&lt;char&gt;(std::basic_string&lt;char&gt;&amp;)&gt;’ { boost::shared_ptr&lt;task_t&gt; example = boost::make_shared&lt;task_t&gt;(boost::bind(&amp;string_with_params, ans)); boost::future&lt;std::string&gt; f = example-&gt;get_future(); boost::thread task(boost::bind(&amp;task_t::operator(), example)); std::string answer = f.get(); std::cout &lt;&lt; "string_with_params: " &lt;&lt; answer &lt;&lt; std::endl; task.join(); } </pre><p> EXAMPLE 7: </p> <pre class="wiki">//Using boost::asio::io_service and boost::bind // error: invalid use of incomplete type ‘class boost::packaged_task(std::basic_string&amp;)&gt;’ // error: incomplete type ‘task_t {aka boost::packaged_task(std::basic_string&amp;)&gt;}’ used in nested name specifier // boost/thread/future.hpp:1320:11: error: declaration of ‘class boost::packaged_task(std::basic_string&amp;)&gt;’ { boost::asio::io_service io_service; boost::thread_group threads; boost::asio::io_service::work work(io_service); for (int i = 0; i &lt; 3; ++i) { threads.create_thread(boost::bind(&amp;boost::asio::io_service::run, &amp;io_service)); } boost::shared_ptr&lt;task_t&gt; example = boost::make_shared&lt;task_t&gt;(boost::bind(&amp;string_with_params, ans)); boost::future&lt;std::string&gt; f = example-&gt;get_future(); io_service.post(boost::bind(&amp;task_t::operator(), example)); std::string answer = f.get(); std::cout &lt;&lt; "string_with_params: " &lt;&lt; answer &lt;&lt; std::endl; threads.join_all(); } </pre><p> It seems like future.hpp has a problem that is preventing the proper template from being used. </p> en-us /htdocs/site/boost.png https://svn.boost.org/trac10/ticket/9303 Trac 1.4.3 anonymous Fri, 25 Oct 2013 18:22:55 GMT https://svn.boost.org/trac10/ticket/9303 https://svn.boost.org/trac10/ticket/9303 <ul> <li><strong>attachment</strong> → <span class="trac-field-new">packagedTestTest.cpp</span> </li> </ul> Ticket viboes Sat, 26 Oct 2013 11:13:22 GMT https://svn.boost.org/trac10/ticket/9303#comment:1 https://svn.boost.org/trac10/ticket/9303#comment:1 <ul> <li><strong>owner</strong> changed from <span class="trac-author">Anthony Williams</span> to <span class="trac-author">viboes</span> </li> <li><strong>status</strong> <span class="trac-field-old">new</span> → <span class="trac-field-new">assigned</span> </li> </ul> <p> This is normal if you are using BOOST_THREAD_VERSION = 2, which is the default. </p> <p> If you can not use BOOST_THREAD_VERSION = 2, use packaged_task&lt;R&gt; instead of packaged_task&lt;R()&gt;, but you couldn't work with non-nullary functions (you must then use boost::bind). </p> <p> Which version are you using? Which compiler? </p> Ticket anonymous Tue, 29 Oct 2013 19:53:04 GMT https://svn.boost.org/trac10/ticket/9303#comment:7 https://svn.boost.org/trac10/ticket/9303#comment:7 <ul> <li><strong>status</strong> <span class="trac-field-old">assigned</span> → <span class="trac-field-new">closed</span> </li> <li><strong>resolution</strong> → <span class="trac-field-new">worksforme</span> </li> <li><strong>milestone</strong> <span class="trac-field-deleted">To Be Determined</span> </li> </ul> <p> Committed the examples with the fixes </p> <p> <a class="ext-link" href="https://github.com/boostorg/thread/commit/7d4f485ade79c0fbb6434402e52045040ef000c9"><span class="icon">​</span>https://github.com/boostorg/thread/commit/7d4f485ade79c0fbb6434402e52045040ef000c9</a> </p> Ticket