Re: [boost] [date-time] [serialization] [graph] [ublas] Boost 1.34.0 Beta released

From: Jeff Garland (jeff_at_[hidden])
Date: 2007-04-29 23:08:15

Kim Barrett wrote:
> At 4:40 PM -0700 4/29/07, Jeff Garland wrote:
>> Domenico Andreoli wrote:
>> diff -ur -x .svn ../boost-1.34.0-beta1/boost/archive/polymorphic_oarchive.hpp
>> ./boost/archive/polymorphic_oarchive.hpp
>>
>> +
>> +    virtual ~polymorphic_oarchive() {}
>>
> 
> For what it's worth, I've been maintaining a similar local patch
> against 1.33.1 and have determined that it needs to be applied to 1.34.0
> as well. Below is the comment associated with the patch:
> 
> +    // kab, 9/26/06: Avoid destructor slicing when using polymorphic archives,
> +    // where clients may not know the precise type. The need for this was
> +    // reported to Robert Ramey (via boost developers list), where he
> +    // acknowledged the problem and said he would fix in a future release.
> +    virtual ~polymorphic_iarchive() { /* nothing to do here */ }
> 
> I believe that date was post-RC_1_34_0 branch, and in fact I think at
> the time it was thought that boost 1.34.0 was immanent.
> 
> Hm. But reviewing the email thread I see that Robert ultimately
> decided not to make this change, for reasons that I didn't (and still
> don't) understand (and apparently forgot to pursue). See:
> 
>    http://lists.boost.org/Archives/boost/2006/09/110979.php

I don't really understand this at all.  I thought the whole point of 
polymorphic_text_*archive was so you could derive from it and re-implement the 
  various load/save methods.  The whole point being that you can write your 
own format and use runtime dispatch ala classical serialization...after a 
quick look, though I guess I don't understand.

> So I would suggest that this might not be a simple and obviously safe
> change for boost 1.34.0.

Actually I find it hard to see how it will do any harm either.  The class 
already has a virtual table so it can't increase the size of an instance.  The 
accessibility isn't changed.  I guess Robert will need to explain...

Jeff