Re: [Boost-users] [Serialization] Runtime error in load_pointer

19 Jan 2010

      elizabeta petreska wrote:
...
Again thank you all who helped me in this .
...
...
This is likely a secondary effect from some other error.
It was secondary error.
...
...
A complete shot in the dark but it is possible it might be the
problem.
This was the problem, so it wasn't shot in the dark at all.
The problem was that my classes have the following class members :
shared_ptr<const T> , vector<const T>, vector
and many others  that have const inside them. I can not remove const
from these, altghough  I wish :)
I was casting const away (http://tinyurl.com/yae5stv ) for all this
members only at the point of loading, for example in many cases I was
saving vector<const T> and loading vector<T>. Now I added const cast
at the point of saving too, so saving and loading is symmetric. It
seems it works Ok now, and I hope this is the right way to solve the
problem.
I'm curious about this.

a) I can't understand why vector<const T> is even valid.  My understanding
is that the value of type of a container must be Assignable and that
a const T is by definition not assignable.  So I would expect this to
show up as an issue long before serialization is involved.

b) I can't see how one gets the asymetry in the first place.  E.G.

class X {
    vector<const T> m_v;
    template<class Archive>
    void save(Archive & ar, const unsigned int version) const {
        ar << m_v;
    }
    template<class Archive>
    void load(Archive & ar, const unsigned int version){
        ar >> m_v;
    }
    ...
};

Hmmm I suppose that one might use a cast on a load but not on the save.
This is a case which in fact I've never considered.  I'll think about this.

Meanwhile, any C++ STL gurus can feel free to comment on a) above.

Robert Ramey