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From: bjorn@alberta.UUCP (Bjorn R. Bjornsson)
Newsgroups: comp.arch
Subject: Re: implementing shared libraries
Message-ID: <301@pembina.UUCP>
Date: Wed, 22-Apr-87 19:59:00 EST
Article-I.D.: pembina.301
Posted: Wed Apr 22 19:59:00 1987
Date-Received: Sat, 25-Apr-87 19:21:20 EST
References: <12823@watnot.UUCP>, <926@aw.sei.cmu.edu.sei.cmu.edu> <7952@utzoo.UUCP>
Organization: U. of Alberta, Edmonton, AB
Lines: 28

In article <7952@utzoo.UUCP>, henry@utzoo.UUCP (Henry Spencer) writes:
> Don't forget the problems of (a) where does static data for the library
> functions live (they need to know this),

I favor having a stub that passes the address of these
(eg. 'errno', '_iob' etc.) linked into each and every
process image.  That way you don't have to touch the linker
(not that Unix linkers couldn't stand to be touched up
{a,"more than a little"} bit B-).  This sort of stuff can
actually be done *without* source code if you're a crack
hack (it helps to have the object modules and 'adb' though).

> and (b) how does the user code
> find out where the foobar() function is.  I think the latter is more what
> the original question was about.

This one is easier yet (if you have shared memory or
default mapping of system address space) and has many
solutions unless the architecture is Unix bound and
specifically forbids executing out of a process' data
segment (assuming System V compatible shared memory here).

		I'm not much of a socialist B-), even
		if I advocate sharing common procedures.
		OR anyone?

			Bjorn R. Bjornsson
			{ubc-vision,ihnp4,mnetor}!alberta!bjorn