Re: [Boost-users] [serialization] Reading back old archives

Subject: Re: [Boost-users] [serialization] Reading back old archives
From: David Raulo (david.raulo_at_[hidden])
Date: 2010-07-18 06:29:31

Hi,

Le 13 juil. 2010 à 14:03, David Raulo a écrit :

> Le 12 juil. 2010 à 22:43, Robert Ramey a écrit :
> 
>> David Raulo wrote:
>>> 
>>> Here you can see that the original version 20090123 got truncated to
>>> 36107 == 20090123 & 65535. This in itself might be a bug, I'm not
>>> sure.
>> 
>> I can't see this.  But I do see how this assertion would be tripped.  If
>> you comment out this assertion does this make it work?
> 
> Then the execution proceeds without exceptions, my serialize() method is 
> called, but I verified that it receives 36107 as the version instead of
> 20090123.

So, what can I do to help?

In my view there are 2 problems:
- since boost 1.42, the version numbers are internally truncated to 16 bits
   when reading archives;  this causes data loss, which the user might
   be able to work around in some cases.

- since boost 1.43, reading these archives will raise an assertion
 (iserializer.hpp:173)  before the user get any chance to work around the
  truncated version numbers.

I addressed the 2d problem in the atttached patch. Comments welcome.

For the first problem, I believe the only solution is to change the definition
of version_type in basic_archive.hpp  back to uint_least32_t.    This would 
fix a data-loss regression, without any downside that I can think of.
Please note that your wish to prevent any new version number bigger than 
255 would still be enforced by the static_assert in serialization/version.hpp 
you introduced with boost 1.43.

Is that acceptable?

Thanks for your help.

David.