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

Subject: Re: [Boost-users] [serialization] Reading back old archives
From: Robert Ramey (ramey_at_[hidden])
Date: 2010-07-18 11:39:52

David Raulo wrote:
> 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?

I have been working on this.  I thought I had it.  I hadn't realized
the the issue arose prior to 1.43.  I think that you're analysis
is correct.  I'll take yet another look at this. Thanks for your patience.

>
> Thanks for your help.
>
> David.
>
>
>
>
>
>
>>
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>
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