on Wed Dec 28 2011, "Robert Ramey" <ramey-AT-rrsd.com> wrote:
The only legal technique I've seen for that is at https://gist.github.com/1528856, and Boost.Serialization should probably have support for that approach.
I looked at this - extremely clever - I expect nothing less from you!
It's not my cleverness; it comes from http://bloglitb.blogspot.com/2010/07/access-to-private-members-thats-easy.ht... (as noted in the Gist title) I had to spend quite some time analyzing that code to figure out what it was doing and why it worked, so I wanted to publish a version with comments.
Actually, too clever in my opinion. Basically we have private: which means "don't let anyone outside of here access this !". This is pretty clear. Then we add: friend boost::serialization::access "which means - make an exception to the above for boost::serialization!". Which is also pretty clear. But your method would let me get my hands on someone else's private members without their giving permission. If this were to happen to me, I don't think I'd like it.
Meh, I don't care. As noted in the comments to http://bloglitb.blogspot.com/2010/07/access-to-private-members-thats-easy.ht..., the point of private is to prevent accidental misuse, not to be some kind of inviolable firewall.
Users have the option of doing this if they want to avoid having to use the friend declaration in some special cases.
Obviously, if you can alter the class declaration to make boost::serialization::access a friend, that's preferable. The point would be to provide the means to serialize even when altering the class declaration was not an option. This ability to gain access non-intrusively might be useful for Boost.Python as well (though usually the problem there is access to a base class virtual function that may well be private, and this technique can only get you access to a virtual function's final override).
So I would be skeptical that something like this would be a good thing to include in the serialization library.
You're the boss. -- Dave Abrahams BoostPro Computing http://www.boostpro.com