Re: [Boost-users] [bind] Will not compile when passing parameter by-value

Subject: Re: [Boost-users] [bind] Will not compile when passing parameter by-value
From: Robert Dailey (rcdailey_at_[hidden])
Date: 2009-08-26 12:41:28

On Wed, Aug 26, 2009 at 11:29 AM, Robert Dailey <rcdailey_at_[hidden]> wrote:

> Hello,
> I have a class called ByteSink that has a move constructor and move
> assignment operator. I pass an object of type ByteSink into bood::bind()
> by-value and it fails to compile. First, here is my call to boost::bind():
>
> void SerialClient::Write( ByteSink data )
> {
>   m_service.post( boost::bind( &SerialClient::DoWrite, this, data ) );
> }
>
> The error message I'm getting will be located at the very bottom of this
> message to prevent clutter. Note that I am compiling on MSVC9 under Windows.
> Below is what my move constructor/assignment function prototypes look like
> for ByteSink:
>
>   /// Uses move semantics.
>   ByteSink( ByteSink& other );
>
>   /// Uses move semantics.
>   ByteSink& operator= ( ByteSink& other );
>
> And the compiler error I'm getting (It's a bit lengthy) is below. Any idea
> what is causing this? My best guess is that boost::bind() is using const
> somewhere, and it cannot find a copy constructor that takes a const ByteSink
> as a parameter, since I'm not using a typical copy constructor.
>
> 1>C:\IT\third_party\boost_1_40_0_beta1\boost/bind/bind.hpp(859) : error
> C2558: class 'boost::_bi::list2<A1,A2>' : no copy constructor available or
> copy constructor is declared 'explicit'
> 1>        with
> 1>        [
> 1>            A1=boost::_bi::value<SerialClient *>,
> 1>            A2=boost::_bi::value<ByteSink>
> 1>        ]
> 1>        C:\IT\third_party\boost_1_40_0_beta1\boost/bind/bind.hpp(859) :
> while compiling class template member function
> 'boost::_bi::bind_t<R,F,L>::bind_t(F,const L &)'
> 1>        with
> 1>        [
> 1>            R=void,
> 1>            F=boost::_mfi::mf1<void,SerialClient,ByteSink>,
> 1>            L=boost::_bi::list2<boost::_bi::value<SerialClient
> *>,boost::_bi::value<ByteSink>>
> 1>        ]
> 1>        ..\SerialClient.cpp(32) : see reference to class template
> instantiation 'boost::_bi::bind_t<R,F,L>' being compiled
> 1>        with
> 1>        [
> 1>            R=void,
> 1>            F=boost::_mfi::mf1<void,SerialClient,ByteSink>,
> 1>            L=boost::_bi::list2<boost::_bi::value<SerialClient
> *>,boost::_bi::value<ByteSink>>
> 1>        ]
>

I just verified that boost::bind() requires ByteSink to have a constructor
of the form:
ByteSink( ByteSink const& )

And it will not accept:

ByteSink( ByteSink& )