[Boost-users] boost::signals - can't generate assignment op.

Subject: [Boost-users] boost::signals - can't generate assignment op.
From: Noah Roberts (roberts.noah_at_[hidden])
Date: 2009-01-27 14:16:27

I know that signals can't be assigned or copied, and as far as I can 
tell I have made sure that never happens.  However, I'm still getting 
the warning.  We have no warning policy here.

Code followed by compiler output, what do I need to do?:

-------------------------------------------
#include <boost/signal.hpp>
#include <boost/function.hpp>

struct rect {};

       struct document
       {
         document() : changed_sig() {}
         virtual rect extents() const = 0;

         virtual ~document() {}

         boost::signals::connection attach(boost::function<void 
(document&)> const& slot)
         {
           return changed_sig.connect(slot);
         }

       private:
         boost::signal<void (document&)> changed_sig;
         document(document const&) {}
         document& operator=(document const&) { return *this;}

       protected:
         void changed(document & d) { changed_sig(d); }
       };

int main()
{
}
------------------------------------------------

1>e:\boostvs2\include\boost\signals\trackable.hpp(163) : warning C4512: 
'boost::signals::detail::bound_objects_visitor' : assignment operator 
could not be generated
1>        e:\boostvs2\include\boost\signals\trackable.hpp(66) : see 
declaration of 'boost::signals::detail::bound_objects_visitor'
1>e:\boostvs2\include\boost\signals\signal_template.hpp(71) : warning 
C4512: 'boost::signals::detail::args1<T1>' : assignment operator could 
not be generated
1>        with
1>        [
1>            T1=document &
1>        ]
1>        e:\boostvs2\include\boost\signals\signal_template.hpp(344) : 
see reference to class template instantiation 
'boost::signals::detail::args1<T1>' being compiled
1>        with
1>        [
1>            T1=document &
1>        ]
1>        e:\boostvs2\include\boost\signals\signal_template.hpp(335) : 
while compiling class template member function 'void 
boost::signal1<R,T1,Combiner,Group,GroupCompare,SlotFunction>::operator 
()(T1)'
1>        with
1>        [
1>            R=void,
1>            T1=document &,
1>            Combiner=boost::last_value<void>,
1>            Group=int,
1>            GroupCompare=std::less<int>,
1>            SlotFunction=boost::function<void (document &)>
1>        ]
1>        e:\boostvs2\include\boost\signal.hpp(335) : see reference to 
class template instantiation 
'boost::signal1<R,T1,Combiner,Group,GroupCompare,SlotFunction>' being 
compiled
1>        with
1>        [
1>            R=void,
1>            T1=document &,
1>            Combiner=boost::last_value<void>,
1>            Group=int,
1>            GroupCompare=std::less<int>,
1>            SlotFunction=boost::function<void (document &)>
1>        ]
1>        e:\dev_workspace\experimental\scratch\scratch\main.cpp(19) : 
see reference to class template instantiation 'boost::signal<Signature>' 
being compiled
1>        with
1>        [
1>            Signature=void (document &)
1>        ]
1>Linking...