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