The incompatibilities that have hit hardest are for the modules that use C language extensions. This can't really be helped for such a major change to the unde

The incompatibilities that have hit hardest are for the modules that use C language extensions. This can't really be helped for such a major change to the underlying structure. The ruby language changes were mostly included in Ruby 1.8.7, and so most "pure ruby" libraries that worked there also work in 1.9.