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From: marbru@auto-trol.UUCP (Martin Brunecky)
Newsgroups: comp.sys.dec,comp.os.vms
Subject: Re: Runtime loading of shareable images
Message-ID: <764@auto-trol.UUCP>
Date: 12 Mar 90 15:44:46 GMT
References: <1062@eastman.UUCP> <27705@cup.portal.com>
Reply-To: marbru@auto-trol.COM (Martin Brunecky)
Distribution: usa
Organization: Auto-trol Technology, Denver
Lines: 30

In article <27705@cup.portal.com> Prodas@cup.portal.com (Henry Lewis Feldman) writes:
>I have a question about run-time dynamic linking.
>
>I am working on a C program that during run-time must choose between
>several different subroutines.  Ideally these run-time subroutines
>should be "shareable images".  But is there a program callable routine
>that will dynamically load an image, my reading of the linker is that
>link to the shareable image is fixed at link time.  My program must choose
>between one of many images after the program has started.
>
>Can anyone point me to the proper routines?

	What about operating system ???

	Assuming VMS, look at LIB$FIND_IMAGE_SYMBOL. Does everything you need.
	Be carefull about logical name for the loaded shareable image.
	Must always be the same, otherwise you may end up with the same image
	loaded multiple times.

	I have a Macro module, acting as a dynamic loader, and a set of tools
	that allow us to build images with "stub" rerferences to dynamically
	called shareable images. At runtime, those stubs are re-built on the
	first request to a particular entry, so that subsequent call overhead 
	on call to an entry in shareable image is 1 JMP instruction, i.e. the
	same as if you bind to shareable image at link time.
-- 
=*= Opinions presented here are solely of my own and not those of Auto-trol =*=
Martin Brunecky                   marbru@auto-trol.COM
(303) 252-2499                    {...}ncar!ico!auto-trol!marbru
Auto-trol Technology Corp. 12500 North Washington St., Denver, CO 80241-2404