Why would one need Software Collections?

Why would one need Software Collections?

I can understand wishing to chose a particular interface for your mail, or wishing to chose a particular implementation for one's ldap, but why would one ever want to have multiple versions of a program?

I quite understand the versioning problem (I co-authored an ACM article on the subject) but with Linux's stable interfaces, there isn't a good reason for incompatability except for bugs, and one can deal with them by symlinking, for example, /usr/bin/bizzare to /usr/bin/bizzare_42.0

And anyone who ships versions of system libraries with applications deserves the sharp edge of Linus' tongue!

Back when I was one of the solarii, my evil twin (David J. Brown) imposed versioning on all library interfaces. If you shipped libfart.2.37.so, and you had changed the semantics (but not the signature) of the so-named library call, you had to ship the old .36 implementation as well as the new .37 implementation. Linkers linked the version that programs were compied for, and compilers defaulted to compiling for the newest.

As soon as he'd ensured that was in place, he prohibited vendors from shipping system libraries (they already weren't supposed to), and greatly reduced the likelyhood of them causing a patching/security problem.

If one installed a "too new" program, it had a dependancy on the latest version of the system library, that got installed, and both old and new programs just quietly worked.

Implementation- and use-choices are legitimate: collections as a way to paper over a bug are not.

--dave

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