Re: [boost] Re: Serialization: docs addition

From: Darren Cook (darren_at_[hidden])
Date: 2005-04-23 03:02:09

> Hmm - what was wrong with the archive being smaller than you wanted?  Since
> your argument is const, it should be the same value.

It is const because BigClass::get_data() returns a const pointer to its
internal data (which is not const).

mycallback() is called repeatedly, as operations happen that change the
data in BigClass.

> dereferencing is not the same as serialization the pointer.  In the second
> case a new object will be created when serialized.  I would be surprised if
> dereferencing eliminated the copy.

No, it worked: I got the data I expected to be serialized.

I realized after posting that doing this may be clearer:
  const SomeData &d=*BC.get_data();

(or get_data() returning a const reference in the first place, but
BigClass works and I don't want to fiddle with it at the moment).

Darren

> 
> Finally, if you really want to write mulltiple copies of the same the item,
> the best way would be to mark objects of this type as "track_never"
> 
> Robert Ramey
> 
> 
> 
> Darren Cook wrote:
> 
>>Hi,
>>Can I suggest adding another example to:
>>http://www.boost.org/libs/serialization/doc/special.html#objecttracking
>>
>>I had this code:
>>
>>void mycallback(const BigClass &BC){
>>const SomeData *d=BC.get_data();
>>...
>>archive & BOOST_SERIALIZATION_NVP(d);
>>}
>>
>>My archive was smaller than intended and I discovered that the data
>>only
>>got saved the first time. XML version showed me it was using:
>>object_id_reference.
>>
>>It turns out the fix was to dereference the pointer:
>>  archive & BOOST_SERIALIZATION_NVP(*d);
>>
>>That is an easy to write bug; I cannot see how the serialization
>>library
>>can catch it, so all I can think of is to make people aware of it in
>>the docs. Also please mention "object_id_reference" in the
>>objecttracking
>>section of the docs, as that was the first thing I googled on and it
>>got
>>no useful hits.
>>
>>Darren
>>
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