Re: Gnat on OpenVMS

[Robert Dewar <robert_dewar@my-dejanews.com>]

In article <1999May22.193351.1@eisner>,
  Kilgallen@eisner.decus.org.nospam wrote:
> It certainly is legally difficult if the contract from DEC
> said not to integrate with the VMS debugger.  Of course that
> contract is only binding on ACT (and DEC), so somebody else
> could make changes to GNAT, although for Robert to suggest
> such an action would probably be bad form.
>
> Larry Kilgallen

Just to clarify, the contract had no clause *forbidding*
integration with the VMS debugger. Rather it insisted on full
integration of GDB, so this is where the majority of the work
went. I think there were the following issues involved:

  1. Digital does not see major long term investment happening
     in the future for the VMS debugger, and so there is an
     advantage in shifting in the GDB direction (a number of
     other work station manufacturers are moving towards GDB
     for the same reasons).

  2. In particular, there was no possibility of finding
     resources at Digital for Ada 95 specific modifications
     to the VMS debugger (remember that Digital's first
     inclination was to completely abandon Ada on VMS and
     push all their customers to DEC Unix, it was only when
     a number of customers notified Digital that this was
     not acceptable, that some attention was given to Ada 95
     on VMS.

  3. Adapting GNAT to use the VMS debugger would have been a
     major work item. Would it have been more expensive than
     adapting GDB? Probably, but who knows, we were never asked
     to bid on that adaptation.

We did in fact do some minimal integration with the VMS
debugger, line numbers and procedure names are compatible,
and you can look at some very simple kinds of data. This was
useful for getting the backtrace to work anyway. But complex
data cannot be viewed.

With some (non-trivial) amount of work, the integration with
VMS debug could be greatly improved. But no one seems interested
in funding this at the current time.

Note that Digital was not unaware of the issues of switching
debuggers. During the formal field test, Bart Nickerson made
it clear that he would never be happy with anything other than
the VMS debugger, and so Digital was quite aware that some
segment of the market would feel this way, and perhaps always
will (VMS users can be quite opinionated :-) like Ada folks :-)

One thing is certain and that is that GDB continues to improve
at a rapid pace, and we have found that most problems reported
have been in the category of bugs that can be fixed in a fairly
straightforward manner. In addition, major improvements to GDB
continue to occur from our work, and also the work at Cygnus,
and several other large companies (I am not sure I can give
names at the current time, but you can expect some interesting
announcements in the near future, both concerning companies
adopting GDB, and concerning the maintenance of GDB itself).

Yes, there will be some people who always will prefer the VMS
debugger, and just as no amount of improvement to VI will woo
away EMACS users, I am sure they will feel that way
indefinitely. But in the long run, we are confident that VMS
Ada users will find that GDB meets their requirements, and
indeed a number of users are finding that it works fine for
them right now.

And by the way Larry, if someone wants to contribute the changes
to make GNAT work better with VMS debug, that would be fine with
us, I would be delighted to see that happen, it is just that ACT
does not begin to have the resources to fund such work itself at
the current time.

Robert Dewar
Ada Core Technologies




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