Re: [Boost-users] Serialization Archive IncompatibilitybetweenBoostVersions

19 May 2009

      Hello Robert

After adding nvp wrappers around all serialize commands, I am able to  
produce the xml archives (attached inclusive diff).

The archive produced using boost 1.37 contains the additional element  
'0. This additional element seems to be  
inserted by the std::vector serialization code. I compared the load  
function in vector.hpp from version 1.35 and 1.37 (see code below).  
The  version 1.37 tries to load the variable item_version that is not  
saved by version 1.35.

Is the condition around the additional code  
(BOOST_SERIALIZATION_VECTOR_VERSION < ar.get_library_version())  
executed wrongly?

David

version 1.35:
template
inline void load(
     Archive & ar,
     std::vector &t,
     const unsigned int /* file_version */,
     mpl::true_
){
     collection_size_type count(t.size());
     ar >> BOOST_SERIALIZATION_NVP(count);
     t.resize(count);
     if (!t.empty())
       ar >> make_array(detail::get_data(t),t.size());
   }

version 1.37:
template
inline void load(
     Archive & ar,
     std::vector &t,
     const unsigned int /* file_version */,
     mpl::true_
){
     collection_size_type count(t.size());
     ar >> BOOST_SERIALIZATION_NVP(count);
     t.resize(count);
     unsigned int item_version=0;
     if(BOOST_SERIALIZATION_VECTOR_VERSION < ar.get_library_version())
         ar >> BOOST_SERIALIZATION_NVP(item_version);
     if (!t.empty())
       ar >> make_array(detail::get_data(t),t.size());
   }

On May 18, 2009, at 6:52 PM, Robert Ramey wrote:
...
This looks useful.
May we presume that you're trying to read this with boost 1.37 and the
exception is thrown?
Note that the the 1.35 version has archive library version #4 while  
1.37 has
archive library version #5 in the top row. The archive library  
version is
changed every time we make a change which might mean that older  
archive have
to be handled differently.  A example where this has happened is  
where we
change the type of the integer which indicates how may items there  
are in a
collection.
In this case, 1.37 (library version # 5)  is expecting data which 1.35
(library version #4) didn't put there. That is, 1.37 is missing some  
code
which looks like:
if(library_version >4)
   ar >> i
...
Of course the rub is to figure out where that is.  The key line  
differs in
that:
1.35 1 12 ...
1.37 1 0 12 ... // extr 0
With your test case I would do the following:
Generate the same two files with the xml_archive.  This should  
reveal what
the extra "0" corresponds to.
With the debugger, trap the program where the exception is thrown.   
This
might reveal the part of code which is throwing this extra "0".   
This is
where the mistake might lie.
Robert Ramey
David Graf wrote:
...
...
Hello Robert
Attached, please find two text archive outputs. The first is
generated using boost version 1.35. The second is generated using
boost version
1.37. Additionally, I attached the diff between these archives.
In this diff, you can safely ignore the second and the last
difference. Those are due to random generated data. We assume that
the exception (see attached stacktrace.txt) is caused by the third
difference.
Do you have any idea why this exception is thrown?
David
...
On Apr 9, 2009, at 6:38 PM, Robert Ramey wrote:
...
This version is declared at the beginning of a serialized archive.
E.g.:
The following beginning of a text archive is serialized with boost
1.37:
22 serialization::archive 5 0 35 ...
Serialized with boost 1.35 it looks like this:
22 serialization::archive 4 0 35 ...
Otherwise, the archives are in my case completely identical.
Somehow, if this version number does not match to the serialized or
archive
version of the used boost library, boost throws an exception.
**** where does this exception get thrown?
Robert Ramey
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