Re: [Boost-users] Serialization: C4308 warning with MSVC9

Subject: Re: [Boost-users] Serialization: C4308 warning with MSVC9
From: Robert Ramey (ramey_at_[hidden])
Date: 2010-05-18 23:57:59

Political Confusion wrote:
> --- On Tue, 5/18/10, Robert Ramey <ramey_at_[hidden]> wrote:
>
>> From: Robert Ramey <ramey_at_[hidden]>
>> Subject: Re: [Boost-users] Serialization: C4308 warning with MSVC9
>> To: boost-users_at_[hidden]
>> Date: Tuesday, May 18, 2010, 10:35 PM
>> Political Confusion wrote:
>>> Political Confusion <politicalconfusion <at>
>> yahoo.com> writes:
>>>
>>>>
>>>> I'm using Boost 1.43 with MSVC9 SP1 and Windows
>> SDK v7 on Windows 7.
>>>> I've
>>> created a class like the "A Very
>>>> Simple Case" example (i.e. added 'access' as
>> friend and a templated
>>>> serialize function). In serialize, I just
>> archive 10 ints (signed
>>>> and unsigned). It compiles fine, but when I add program code to
>>>> save my class to a text_oarchive, I get a warning:
>>>>
>>>>
>> c:\third-party\boost_1_43_0\boost\mpl\print.hpp(51) :
>> warning C4308:
>>>> negative integral constant converted to unsigned
>> type
>>>>
>>>> Line 51 of print.hpp is: enum { n = sizeof(T) + -1
>> };
>>>>
>>>> Calling sizeof() on my class gives a 44. I
>> do not get any warning
>>>> when I load
>>> my class with text_iarchive. And
>>>> both save and load appear to work fine.
>>>>
>>>
>>> I had to add the following to make this warning go
>> away:
>>>
>>> BOOST_CLASS_TRACKING( my_class,
>> boost::serialization::track_never )
>>
>> This warning should precede a long call chain. If you
>> go to the the
>> call BEFORE this, you should find a comment which indicates
>> why this
>> warning is invoked.
>>
>> Robert Ramey
>>
>>
>>
>> _______________________________________________
>> Boost-users mailing list
>> Boost-users_at_[hidden]
>> http://lists.boost.org/mailman/listinfo.cgi/boost-users
>>
>
> Hello Robert,
>
> That's what I did.  The lines above the warning
> (boost/archive/detail/check.hpp(98)):
>
>     // saving an non-const object of a type not marked "track_never)
>
>     // may be an indicator of an error usage of the
>     // serialization library and should be double checked.
>     // See documentation on object tracking.  Also, see the
>     // "rationale" section of the documenation
>     // for motivation for this checking.
>
>     BOOST_STATIC_WARNING(typex::value);
>
> So I added the BOOST_CLASS_TRACKING() line.  I get the same warning
> if I modify save_schedule() in demo.cpp to instantiate a gps_position
> and save it to oa.  gps_position was the example I used for my class.
>
> Thanks for the reply and thanks for your work.

But this begs the real question.  Do you want tracking or don't you.

Without tracking -
     you won't be able to serialize apointer.
    and you'll missing the opptimization of space if the same object is 
serialized more than once.
    It will be faster to save and restore
With tracking
    The opposite will be true

So the decision to use tracking shouldn't made  as to the easiest way to fix 
the warning.
The other way is to make the object we're saving non-const.

Robert Ramey