Path: utzoo!mnetor!tmsoft!torsqnt!news-server.csri.toronto.edu!helios.physics.utoronto.ca!ists!yunexus!davecb From: davecb@yunexus.YorkU.CA (David Collier-Brown) Newsgroups: comp.unix.ultrix Subject: Re: SunOS vs. Ultrix comparison Keywords: SunOS shareable libraries Message-ID: <21236@yunexus.YorkU.CA> Date: 27 Jan 91 20:04:03 GMT References: <8012@castle.ed.ac.uk> <1991Jan24.074910.6738@pa.dec.com> <518@decvax.decvax.dec.com.UUCP> <2380@shodha.enet.dec.com> Distribution: comp Organization: York U. Computing Services Lines: 36 alan@shodha.enet.dec.com ( Alan's Home for Wayward Notes File.) writes: | IF you trust the vendor not to change the function and interface | to the parts of shared library, then the Q/A is easy. As long | as it still runs then it probably runs correctly. The problems | come if the vendor changes the function of something so that it | isn't quite the same as before. Or changes the size of data | structure. Presumably the vendor will have a method of applying | version numbers to shared libraries that the dynamic load checks | to make that things haven't changed (ident mismatch in VMSese). This does not appear to be implemented **or implementable** with an unchanged sun/bsd interface... | Even if the vendor uses these version numbers correctly, if they | change the version numbers to often (every new release or maybe | every other release) it requires the 3rd party company to re-link | at each library change. And if you have to re-link you have to | re-test. Compatable roll-forward and -back is a known solved problem in computer science **for cases of a client program requesting a service via an invariant interface**. The tricky part is evolving an interface, which tends to cause one to pore over lint output. This may be solved in the domain of formal spcification of the interface, where a change in the specification can yield, by a somewhat exhaustive procedure, a partial specification of the change required to the code. I just don't know if anyone has done the work yet... --dave -- David Collier-Brown, | davecb@Nexus.YorkU.CA | lethe!dave 72 Abitibi Ave., | Willowdale, Ontario, | Even cannibals don't usually eat their CANADA. 416-223-8968 | friends.