Markus Henschel wrote:
Hello,
in its current state boost serialization isn't able to read binary archives from older versions. The documentation states that there is a problem with version 1.42-1.44 but this is not the whole story. My archives from 1.34 don't work either. There are currently open bugs for this:
https://svn.boost.org/trac/boost/ticket/4903 https://svn.boost.org/trac/boost/ticket/5567 https://svn.boost.org/trac/boost/ticket/4660
This situation has been like this for a very long time now. Comments of users even suggest not using binary archives or switching to another serialization library because of maintenance problems. I'm posting to this list as it seems like no one cares about these bug reports anymore. The least thing that should be done I think is to update the release notes. There are even patches in the bug reports that provide fixes although I don't know if they work for all situations. The current situation is quite uncomfortable for me as I have to patch every new boost version to get serialization working.
What can be done to improve this situation?
I've left these open because I don't have a definitive fix. This came about when I made some changes just to eliminate some warnings when used for some compilers. I considered these changes inconcequential (just fixing warnings after all) so I didn't bother incrementing the serialization library layout index in the header record. Well, fixing these warnings had some unintended side effects which changed the archive format. This prevented reliable loading of binary archives for previous version. Of course this took a while to see where this was coming from so even another version went by - this time with a number. Serialization library testing was sufficiently exhaustive to detect this in time and it took a while to pin down. Naturally I expect to be much more careful in the future. I'm very much aware that this creates a problem for some users but I've concluded that I can't make any change in the library that will really fix it. It's not totally hopeless however. Would the following procedure work for you? a) using boost 1.34 make small program which i) loads the binary archives into memory using boost 1.34 ii) saves the data loaded above using text_archive or portable_binary_archive. b) using boost 1.49+ make a small program which i) loads the text_archive created in step a) above ii) saves the data loaded above to a new binary_archive. I believe this would permanently fix the problem. And I promise to be more careful in the future. A couple of misc notes on this subject. a) this situation occured because I made a mistake while updated the boost serialization library. But it could occur from other sources - example a compiler upgrade which changes the properties of some primitive datatype. So I would recommend using text or portable binary archives for storage to disk and reserver binary_archives for temporay archives. b) I would like to enhance and make more robust the archive aspects of the boost serialization library but I'm a little "gun-shy" after this experience. The main problem is that I don't a good set of tests for backward compatibility, making such tests would require a non-trivial effort, and I feel the serialization library already places a disproportionately large burden on the boost testing infrastucture. This discourages me from adding some necessary enancements like yaml, json archives and archives which create xml dtd/schema to permit editing with xml tools and archives which save/load to/from GUIs like mfc, qt, wxWindows, html5, etc. I do maintain the library and have relatively few issues because it's not hard to do. Unfortunately, the best I can do for your issue is what I've suggested above. I hope you appreciate that it is embarassing for me to confess to all this. Robert Ramey
Thanks,
Markus Henschel
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