[Boost-bugs] [Boost C++ Libraries] #5640: serialization vector backward compatibility problem

Subject: [Boost-bugs] [Boost C++ Libraries] #5640: serialization vector backward compatibility problem
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-06-24 21:17:06

#5640: serialization vector backward compatibility problem
---------------------------------+------------------------------------------
 Reporter:  jfaust@…             |       Owner:  ramey        
     Type:  Bugs                 |      Status:  new          
Milestone:  To Be Determined     |   Component:  serialization
  Version:  Boost 1.46.1         |    Severity:  Regression   
 Keywords:                       |  
---------------------------------+------------------------------------------
 We've recently upgraded from 1.40.0 to 1.46.1 and uncovered the following
 problem with vector serialization.

 In 1.40.0, the code to load a vector is:

 {{{
 #ifndef BOOST_SERIALIZATION_VECTOR_VERSION
 #define BOOST_SERIALIZATION_VECTOR_VERSION 4
 #endif
 ...
 template<class Archive, class U, class Allocator>
 inline void load(
     Archive & ar,
     std::vector<U, Allocator> &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());
   }
 }}}

 In 1.46.1, the same method is

 {{{
 #ifndef BOOST_SERIALIZATION_VECTOR_VERSIONED
 #define BOOST_SERIALIZATION_VECTOR_VERSIONED(V) (V==4 || V==5)
 #endif
 ...
 template<class Archive, class U, class Allocator>
 inline void load(
     Archive & ar,
     std::vector<U, Allocator> &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_VERSIONED(ar.get_library_version())) {
         ar >> BOOST_SERIALIZATION_NVP(item_version);
     }
     if (!t.empty())
         ar >> make_array(detail::get_data(t),t.size());
   }
 }}}

 Look at the difference when reading in a vector from serialization library
 version 4.  In 1.40.0, the logic assumes that versions greater than 4
 should read in item_version.  In 1.46.1, the logic assumes that versions
 equal to 4 or 5 should read in item_version.  So, if restoring a file
 saved with version 4, 1.40.0 will not ready in item_version but 1.46.1
 will.

 We are working around this issue with a trick similar to the header
 vector_135.hpp, but would like to see this fixed in an upcoming release.

 After some research, I found this change was made with changeset 55415 for
 ticket 2271.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5640>
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