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From: ford@crash.CTS.COM (Michael Ditto)
Newsgroups: comp.sys.amiga,comp.sys.atari.st,comp.sys.m6809
Subject: Re: Re: True Multitasking, and shared code
Message-ID: <1221@crash.CTS.COM>
Date: Sat, 13-Jun-87 00:46:30 EDT
Article-I.D.: crash.1221
Posted: Sat Jun 13 00:46:30 1987
Date-Received: Sat, 20-Jun-87 20:10:28 EDT
References: <8706040024.AA10895@cogsci.berkeley.edu> <2194@husc6.UUCP> <1206@crash.CTS.COM> <3934@jade.BERKELEY.EDU>
Reply-To: ford@crash.CTS.COM (Michael "Ford" Ditto)
Organization: Crash TS, El Cajon, CA
Lines: 26
Keywords: shared text code libraries UNIX
Xref: mnetor comp.sys.amiga:5734 comp.sys.atari.st:4010 comp.sys.m6809:347

In article <3934@jade.BERKELEY.EDU> mwm@eris.BERKELEY.EDU (Mike (My watch has windows) Meyer) writes:
>Last time I looked (last year at the Atlanta Usenix), the SysV
>libraries required root privs to install (DCL_SYS_ ... oops, sorry;
>had a VMS flashback). This was because the memory allocation for
>shared memory for a shared library had to be fixed.

You do not need to be root to create or install a shared library (unless you
want to replace, for example, the "libc" shared library; this would be like
wanting to replace /bin/sh 8-).  You have to specify at link time the pathname
of the shared portion of the library.  If you want to be able to change this
file, you must put it somewhere such that you can have write permission.
I'm not sure what you mean about the memory allocation, but there is a
limitation in that area -- a given shared library must have a fixed virtual
address, and (obviously) no two shared libraries that are used by the SAME
process can overlap.  This usually means that when you are creating a new
shared library you just look at what areas are available and pick one that
you like, on the (safe) assumption that all libraries could possibly be used
by one program.  If you for some reason run out of vertual address space, you
can really stop and figure out which libraries will never both be needed by the
same program, and make them share addresses.  This is, however, crufty and not
easily automated (I hate to think about trying to build a Makefile that would
do this to install a program).

						-=] Ford [=-
						ford@crash.CTS.COM
						ford%oz@prep.mit.ai.edu