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

Subject: [Boost-users] [serialization] Reading back old archives
From: David Raulo (david.raulo_at_[hidden])
Date: 2010-07-11 13:16:56

Hello,

I have a problem reading back serialization archives generated by older version of boost. I used to have a YYYYMMDD class versioning scheme. This broke with boost 1.42, which truncates the class version numbers to 16 bits, causing my code to generated corrupted archives.  I fixed my code by implementing my own class versioning when compiling with boost 1.42, so I am again able to create archives that I can read back. Unfortunately this fixes only half of the problem.  How can I  read back archives that were saved using older releases of the serialization library?

I saw that someone else opened ticket  3990 for the same problem.  Here you suggested using the function get_library_version() in the following way:

template<class Archive>
void serialization(Archive & ar, unsigned int version){
    library_version_type library_version = get_library_version
    if(library_version < 6)
        // the library version is a date
        my_date = version;
    else{
        // don't use the boost serialization number, use ours instead
        ar & my_date;
    }
    ar && old_data_items
    if(ar.is_loading)
       if(my_date > "jan 10, 2010")
           ar & new_data_item;   

but I can't get this to work:  the version argument is already truncated, and can't be interpreted as a date. As the bug reporter said, this is a case of data loss.  Should I reopen ticket 3990, or is this code supposed to work with svn  (I admit I did not test the trunk)?

Thanks for your help,

David.