I am trying out trunk and the std::packaged_task in C++11. I found an example on usage at http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2709.html but are unable to make it work. I wonder if it is the example or if it is the libstdc++ playing up. #include <iostream> #include <future> #include <thread> template<typename F> std::future<typename std::result_of<F()>::type> spawn_task(F f) { typedef typename std::result_of<F()>::type result_type; std::packaged_task<result_type()> task(std::move(f)); std::future<result_type> res(task.get_future()); std::thread(std::move(task)); return res; } int get_res() { return 42; } int main() { auto f = spawn_task(get_res); std::cout << "Res = " << f.get() << std::endl; } $ /opt/gcc/gcc-trunk/bin/g++ -Wall -Wextra -O2 -std=gnu++0x packaged_task_example.cpp In file included from /opt/gcc/gcc-trunk/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0/functional:56:0, from /opt/gcc/gcc-trunk/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0/future:38, from packaged_task_example.cpp:2: /opt/gcc/gcc-trunk/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0/tuple: In instantiation of ‘struct std::_Tuple_impl<0ul, std::packaged_task<int()> >’: /opt/gcc/gcc-trunk/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0/tuple:398:11: required from ‘class std::tuple<std::packaged_task<int()> >’ /opt/gcc/gcc-trunk/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0/functional:1546:39: required from ‘struct std::_Bind_simple<std::packaged_task<int()>()>’ /opt/gcc/gcc-trunk/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0/thread:133:9: required from ‘std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = std::packaged_task<int()>; _Args = {}]’ packaged_task_example.cpp:12:5: required from ‘std::future<typename std::result_of<F()>::type> spawn_task(F) [with F = int (*)(); typename std::result_of<F()>::type = int]’ packaged_task_example.cpp:25:29: required from here /opt/gcc/gcc-trunk/lib/gcc/x86_64-unknown-linux-gnu/4.7.0/../../../../include/c++/4.7.0/tuple:274:17: error: ‘constexpr std::_Tuple_impl<_Idx, _Head, _Tail ...>::_Tuple_impl(const std::_Tuple_impl<_Idx, _Head, _Tail ...>&) [with long unsigned int _Idx = 0ul; _Head = std::packaged_task<int()>; _Tail = {}; std::_Tuple_impl<_Idx, _Head, _Tail ...> = std::_Tuple_impl<0ul, std::packaged_task<int()> >]’ declared to take const reference, but implicit declaration would take non-const Thanks, -- Lgb
