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From: firth@sei.cmu.edu (Robert Firth)
Newsgroups: comp.arch
Subject: Re: implementing shared libraries
Message-ID: <926@aw.sei.cmu.edu.sei.cmu.edu>
Date: Mon, 13-Apr-87 09:33:06 EST
Article-I.D.: aw.926
Posted: Mon Apr 13 09:33:06 1987
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In article <12823@watnot.UUCP> ccplumb@watnot.UUCP (Colin Plumb) writes:
>In comp.sys.amiga, there's a discussion going on about adding MMU's to
>the machine.  One problem is the Amiga's use of (shared) libraries.
>
>How are they handled on machines with address translation?  Do they just
>have to be written relocatable, or are assignments to virtual memory slots
>done at compile time (yuk), or is there some other technique for fitting
>them into the address spaces of various processes?
>
>If it helps, the Amiga uses an `openlibrary' call which returns a pointer
>to a table of pointers to library routines.  Routines are located at known
>offsets.

Far and away the simplest way is for the compiler to generate
Position Independent Code.  The libraries can then reside at
any place in the process' virtual address space.  They need not
be at the same place in all processes.

Your tame compiler writer should understand the principles of
PIC and the ways to achieve it.  If not, mail me.