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From: rick@svedberg.bcm.tmc.edu (Richard H. Miller)
Newsgroups: comp.lang.c
Subject: Re: linkers (was MAJOR ANSI C FLAW)
Message-ID: <414@uni2.bcm.tmc.edu>
Date: Mon, 2-Nov-87 17:43:38 EST
Article-I.D.: uni2.414
Posted: Mon Nov  2 17:43:38 1987
Date-Received: Fri, 6-Nov-87 04:23:02 EST
References: <1132@gilsys.UUCP> <1246@bsu-cs.UUCP> <6543@brl-smoke.ARPA> <1678@geac.UUCP>
Sender: Unknown@bcm.tmc.edu
Lines: 19
Keywords: linkers name-length
Summary: linkers & upgrades

In article <1678@geac.UUCP>, daveb@geac.UUCP writes:
> 
>   Actually its fairly easy to change a linker (you add a record type,
> however un-unix-like that might sound)
>   What is hard is doing it *quickly*.  You have to wait (on average)
> about three releases before dropping support for the old stuff.
> 
Actually, you probably will not ever be able to drop 'old' stuff. In the
mainframe environment I use (OS-1100), we seem to usually get around this
by having 'new' language compilers output relocatable files with version
numbers in the header. (In this case, 'old' relocatable files would have
a lower version number or non-existent version number in them). The
linker is smart enough to understand that it is working with old style
code and uses the rules established for them to build executable code. Thus 
we can link in relocatable modules many years old without having to recompile
them. (We have some relocatable modules which haven't been compiled for 10
years). This seems like a useful solution to allow the use of 'old' code 
and still add functionality and take advantage of newer techniques, languages,
etc.)