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From: roy@phri.UUCP (Roy Smith)
Newsgroups: comp.arch,comp.unix.wizards,comp.os.misc
Subject: Shared libraries (Was: Re: Big Programs Hurt Performance)
Message-ID: <2903@phri.UUCP>
Date: Tue, 22-Sep-87 10:35:32 EDT
Article-I.D.: phri.2903
Posted: Tue Sep 22 10:35:32 1987
Date-Received: Thu, 24-Sep-87 07:22:01 EDT
References: <6886@eddie.MIT.EDU) <2501@xanth.UUCP> <2067@sfsup.UUCP>
Reply-To: roy@phri.UUCP (Roy Smith)
Organization: Public Health Research Inst. (NY, NY)
Lines: 21
Xref: mnetor comp.arch:2304 comp.unix.wizards:4415 comp.os.misc:213

In article <2067@sfsup.UUCP> shap@sfsup.UUCP (J.S.Shapiro) gives a pretty
good introductory rundown on shared libraries.

	One thing that has always bothered me about shared libraries (or
dynamic loading, if you prefer) is the problem of backward compatability.
It's not too uncommon that a new version of a program comes along, but some
people still want to use the old version, for whatever reason.  Let's say a
new version of scanf comes along which follows some standard a bit closer
than the old one.  This is arguably a good thing, but what if I just happen
to have a program which depends on the old (albeit wrong) behavior of the
scanf library function.

	On a compile-time library loading system, all I would have to do
would be to keep around a copy of the executable loaded with the old
library and I'd be happy.  We have more than one 3.0 binary running on our
SunOS-3.2 systems for exactly this reason.  What do I do on a shared
library system when scanf changes out from under me and breaks my program?
-- 
Roy Smith, {allegra,cmcl2,philabs}!phri!roy
System Administrator, Public Health Research Institute
455 First Avenue, New York, NY 10016