Sohail Somani wrote:
On Thu, 2007-21-06 at 17:56 +0000, Jared McIntyre wrote:
I changed ARCHIVE_VERSION in basic_archive.cpp to 3 (from 4) and this worked for me. Luckily, I'm not using any collections whose serialization format has changed.
Even if you are, shouldn't it be class_version that matters *not* the serialization library version?
a subtle but important distinction. versions numbers are generally attributes of the class definition/declaration. Including version information with class serialzation can include a small performance penalty and I thought it reasonable for STL serialization to never change (silly me). So I left the STL serializations unversioned. When it came time to change the STL serializations - I had to bump the "global" library version and use that number to branch code. The funny thing about this is that I branched the "save" code as well as the "load" code. (except in optional.hpp). I know I did this without thinking about it, I just implemented symetry out of habit. SO I see now that with relatively small effort - adding a function to the output archive interfac - set_library_version(int) - one could generate backward compatible archives. Except for one thing - the classes which store thier versions along with the class. In order to implement this one would do the following: a) implement "version awareness" for the classes "save" functions. I would guess the difficulty of this would depend upon the features of the already implemented serialization. b) replace the BOOST_CLASS_VERSION(<class name>, <latest class version>) with BOOST_CLASS_VERSION(<class name>, <older class version>). I presume that those who do this would make them selves some pre-processor code which invokes the correct version macro. I suspect this might not be doable with some of more complex serializatons such as shared_ptr - but anyway. All this actually turns out to be kind of amazing to me and totally unexpected. If someone thinks this is interesting and/or important enough to make demo/test along with an addition to the documentation (see - case studies), I would be willing to make the minor changes in the code to support this. Robert Ramey
Sohail
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