[Info-vax] VMS porting/rewrite, was: Re: [OT] Wirth style languages, was: Re: Obscure Ada compiler vendors?

[Paul Sture]

In article <kk11j5$etr$1 at dont-email.me>,
 Simon Clubley <clubley at remove_me.eisner.decus.org-Earth.UFP> wrote:

> On 2013-04-08, Keith Parris <keithparris_deletethis at yahoo.com> wrote:
> > On 4/4/2013 11:01 AM, Stephen Hoffman wrote:
> >> Rewriting all of OpenVMS?  That'd lead me to this state:
> >> <http://www.youtube.com/watch?v=3L6i5AwVAbs>. Even if you were to be
> >> successful with a rewrite, once you're done with that very substantial
> >> and years-long effort and investment, you would have something
> >> approximating current-day VMS. Not the features and functions that
> >> folks would would want and would expect after all those years.
> > ...
> 
> This is talking about a rewrite of the code from the ground up, maintaining
> user level API compatibility, but with different and more modern internals.
> 
> >> The rest of the
> >> market is not standing still here, and you're talking about a project
> >> that took three or five years last time (Alpha to Itanium) for a fairly
> >> straight port with very few changes, and with an engineering team that
> >> was very familiar with VMS assigned to the effort full-time.   ~Thirty
> >> million lines of Bliss and C and Macro32 is a huge project to
> >> reconstitute.
> 
> This is talking about a port of the existing code base to a new
> architecture.
> 
> These are two separate issues and people are mixing them up.
> Which one are you thinking of Keith ? (This confusion showed up on the
> mailing list as well, so I think it's important to know exactly what
> you are thinking about here.)
> 
> >
> > By this logic, the GNU project and Linux could never have caught up 
> > with, much less surpassed or exceeded, UNIX capabilities.
> 
> The GNU project started out as building a compiler and replacing vendor
> specific versions of Unix commands/utilities with their own. (Unix makes
> it easy to replace things a bit at a time; VMS does not.)
> 
> However, the GNU project's own OS project, Hurd, stalled during development.

Did it end up at Oracle? :-)

> Linux is far cleaner internally than VMS is (when it comes to porting),
> with a clean separation of architecture specific and non-specific
> components, and was written from the beginning in a portable language.
> 
> As I mentioned on the mailing list recently, a group of university
> students could probably port Linux to a new architecture in a reasonable
> amount of time. That is simply not going to happen with the existing
> VMS code base.
> 
> Furthermore, plugging new components into Linux or another Unix OS is
> easy, especially at user (ie: non-privileged) level because the Unix
> API is designed around the concept of lots of separate programs doing
> their own thing, but linked together by well defined and _public_
> interfaces.
> 
> For example, writing a new shell for Linux is relatively easy. How does
> that compare to replacing DCL on VMS ?

I got the impression in the V2 era that it should be possible to plug 
your own file system into VMS, and the hooks were there for your own CLI 
(the /CLI= qualifier for the username prompt during login and 
AUTHORIZE.EXE).  IIRC a recent discussion here pointed out that the 
latter wasn't publicly documented.

> Since porting the existing code base does not appear to be viable, that
> leaves a new implementation which maintains the user level VMS API,
> but with very different internals.
> 
> There was a experiment carried out in the 1990s with porting VAX/VMS to
> a microkernel architecture using Mach. This was not a port of VMS to
> another hardware architecture (the Mach microkernel ran on a VAX in
> this case) and the result was not even remotely production ready,
> but it did cover some of the issues which would be encountered.
> 
> I read the paper which came out of that research again this weekend and
> it's worthwhile for anyone interested in this subject to actually read.
> I only have the original PS version, but Paul has a PDF version on his
> website at http://www.sture.ch/vms/Usenix_VMS-on-Mach.pdf

I think it's time to re-read that myself.

If anyone wants it the original .PS file is available at:

ftp://ftp.nvg.ntnu.no/pub/vms/freevms/Usenix_VMS-on-Mach.PS

-- 
Paul Sture