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From: tp@ndm20
Newsgroups: net.arch
Subject: Re: Linking Time
Message-ID: <34500003@ndm20>
Date: Wed, 21-May-86 10:19:00 EDT
Article-I.D.: ndm20.34500003
Posted: Wed May 21 10:19:00 1986
Date-Received: Sun, 25-May-86 13:08:15 EDT
References: <219@zeus.UUCP>
Lines: 29
Nf-ID: #R:zeus.UUCP:219:ndm20:34500003:000:1408
Nf-From: ndm20!tp    May 21 09:19:00 1986


>>I work with very large programs that are under constant development. Much
>>time is spent waiting for them to be relinked after a modification to a
>>small number of modules.
> 
>This is handled pretty well in VAX/VMS with linkable images.  By
>maintaining a table of entry points at a constant location in the
>linkable image (typically at the beginning), programs which call
>routines in that image don't need to be relinked when that image (or a
>routine in it) is updated.

That only works if you have a stable library to make an image of.  If
you are just doing development and want to be  able to  make a change
to any module, VMS doesn't do it any better than any other system.  I
read somewhere that the NS32000 cpu has hardware support  for this by
calling modules  through a  jump table,  but you  still need software
support so you can modify  the jump  table and  link in  just the new
routines  (i.e.   change the  jump table  pointer for  the routine to
point to the new version, and then satisfy only the references in the
new routine, and you  will have  a newly  linked version.   You would
only have to do a link from  scratch when  the executable  got to big
for your (or your loader!)'s taste.)

Terry Poot
Nathan D. Maier Consulting Engineers
(214)739-4741
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