Subject: Re: [boost] [serialization] problems implementing free-standingfunctions
From: Thorsten Ottosen (thorsten.ottosen_at_[hidden])
Date: 2009-03-04 13:32:24
Robert Ramey skrev:
>> Why do I need to store the object locally first?
> Of course the easy answer is that the make_nvp takes a reference
> and the compiler flags an error the conversion of an temporary
> item on the stack as an error. But of course you knew that.
> The real question is, "Why does make_nvp (and other wrappers)
> take only references rather than copying real values". Here a couple of
> a) All parameters in the serialization library are passed by reference.
> This is necessary to support tracking for those situations which
> require it. It would be confusing if support of tracking were
> a hidden side effect of how an argument has been passed.
> b) make_nvp is a wrapper. The concept of a wrapper is to
> add some extra "sauce" (in this case, the external name of the
> data item") while leaving original operations the same. This
> is the case with all wrappers. That is, a wrapper doesn't
> change things, it just adds something. This permits one
> to keep in his brain what is really going on. Also it permits
> one to nest wrappers to any resonable depth.
> c) passing by reference is going to be more efficient for
> larger structures.
> d) not all structures have copy constructors
> FWIW, Lately, I've had occasion to consider this question in more
> depth and can see how elaborating this issue might make the
> serialization library useful in new domains. However this is
> outside of the scope of this discussion.
After thinking a little about it I guess it is quite ok, since
we don't want to serialize temporary objects by accident.
I can't get the error that I though I was getting about not being
able to serialize non-const objects. I guess it was just the above error
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk