Path: utzoo!attcan!uunet!clyde.concordia.ca!news-server.csri.toronto.edu!rutgers!usc!elroy.jpl.nasa.gov!ames!amelia!roelofs
From: roelofs@amelia.nas.nasa.gov (Cave Newt)
Newsgroups: comp.os.msdos.programmer
Subject: Re: Overlays
Keywords: linker overlay
Message-ID: <7542@amelia.nas.nasa.gov>
Date: 27 Jul 90 08:03:43 GMT
Organization: University of Chicago
Lines: 31

bert@neptune.iex.com (Bert Campbell) writes:

>I'm using MSC 5.0 and the linker that is supplied with it (3.61)
>to create overlays in a big large-model program.  At first I couldn't
>get them to work at all, but we finally figured out that functions in overlays
>called via a function pointer wouldn't work with this linker.  Along with
>that are other limitations that make a better linker a requirement.

I'm assuming that, as an MSC developer, you've recently received an offer
from Pocket Soft to purchase .RTLink at a substantial discount (few weeks
ago?  If not, give them a call).  They do get rid of the function pointer
problem, at least.

>I'm looking for general experiences with other linkers for creating
>large "heavily overlayed" programs.  Recommendations for a particular
>linker (RTLink? PLink?) with accompanying reasons would be a help.
>
>In partiicular, do any of the "advanced" linkers allow you to put
>the same object in more than one overlay?  Other pitfalls to look out for?

I haven't tried .RTLink, but their brochure mentions hierarchical overlays,
which is effectively what you're asking about:  the "same object" goes
in the parent overlay, and the rest of your routines go in two or more
sub-areas.  It's not clear from the documentation whether the nesting is
limited to a total of three levels, or if it's unlimited.  

And if you wait a month or two, you can just use the "virtual memory
linking" of version 4.0, which sounds a bit more flexible.

I've no connection with Pocket Soft, btw; just impressed by the sales
pitch. :)