2013/6/1 Vicente J. Botet Escriba <vicente.botet@wanadoo.fr> I don't find a constructor of function from a rvalue functor.
From the standard: template<class F> function(F f); template <class F, class A> function(allocator_arg_t, const A& a, F f); 7 Requires: F shall be *CopyConstructible*. f shall be Callable (20.10.11.2) for argument types ArgTypes and return type R. The copy constructor and destructor of A shall not throw exceptions. 8 Postconditions: !*this if any of the following hold: — f is a NULL function pointer. — f is a NULL pointer to member. — F is an instance of the function class template, and !f 9 Otherwise, *this targets a copy of f initialized with std::move(f). [Note: Implementations are encouraged to avoid the use of dynamically allocated memory for small callable objects, for example, where f’s target is an object holding only a pointer or reference to an object and a member function pointer. — end note ] 10 Throws: shall not throw exceptions when f is a function pointer or a reference_wrapper<T> for some T. Otherwise, may throw bad_alloc or any exception thrown by F’s copy or move constructor.
But I find an assignment
template<class F> function& operator=(F&& f); 18 Effects: function(std::forward<F>(f)).swap(*this); 19 Returns: *this
This seems confusing. What am I missing?
I don't have a standard but this is in sync what you describe: http://en.cppreference.com/w/cpp/utility/functional/function/function http://en.cppreference.com/w/cpp/utility/functional/function/operator%3D confusing indeed. Anyway, trying to: #define BOOST_THREAD_VERSION 4 #include <boost/thread/future.hpp> #include <functional> int main() { boost::packaged_task<void()> t; std::function<void()> f2; f2 = std::move(t); } gives exactly the same compilation error: 1>------ Build started: Project: ConsoleApplication2, Configuration: Debug Win32 ------ 1> main.cpp 1>c:\program files (x86)\microsoft visual studio 11.0\vc\include\xrefwrap(317): error C2248: 'boost::packaged_task<<unnamed-symbol>>::packaged_task' : cannot access private member declared in class 'boost::packaged_task<<unnamed-symbol>>' 1> with 1> [ 1> <unnamed-symbol>=void (void) 1> ] 1> d:\devel\boost_1_54_0_beta1\boost\thread\future.hpp(2783) : see declaration of 'boost::packaged_task<<unnamed-symbol>>::packaged_task' 1> with 1> [ 1> <unnamed-symbol>=void (void) 1> ] 1> c:\program files (x86)\microsoft visual studio 11.0\vc\include\xrefwrap(404) : see reference to function template instantiation 'std::_Callable_base<_Ty,_Indirect>::_Callable_base<_Ty&>(_Ty2)' being compiled 1> with 1> [ 1> _Ty=boost::packaged_task<void (void)>, 1> _Indirect=false, 1> _Ty2=boost::packaged_task<void (void)> & 1> ] but that might as well be VC2012 bug as there is plenty :/ Regards, Simon