Path: utzoo!mnetor!uunet!lll-winken!lll-lcc!ames!pasteur!ucbvax!CITHEX.CALTECH.EDU!carl
From: carl@CITHEX.CALTECH.EDU (Carl J Lydick)
Newsgroups: comp.os.vms
Subject: Re: question on chaining images
Message-ID: <880313025925.343@CitHex.Caltech.Edu>
Date: 13 Mar 88 11:02:49 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 15


 > I am looking for a system service or run-time library routine that
 > will allow me to execute a second image.  I want to do this in such
 > a way that the flow of control will pass entirely to the second image,
 > and will return to the first image at the calling point after the second image
 > completes. Neither CREPRC nor LIB$SPAWN seem to do this, which makes sense
 > since their purpose is to create another process altogether.  I just want the
 > SAME process to start executing a second image.  I'm sure I'm overlooking
 > something obvious...

First, I have to complain about your nomenclature: when you "chain" an image,
control passes entirely from the image you're currently running, and when
the "chained" image exits, control reverts to the OS (in the case of VMS,
generally DCL).  To do what you want to do, the image to be invoked must
be sharable, and you invoke it by using LIB$FIND_IMAGE_SYMBOL, then branching
to the entry point you want to use.