Re: Green Hills Ada library question (Ada on VxWorks)

[dewarr@my-dejanews.com]

In article <98092209530702@psavax.pwfl.com>,
  "Marin David Condic, 561.796.8997, M/S 731-96" <condicma@PWFL.COM> wrote:
> dewarr@MY-DEJANEWS.COM writes:
> >One interesting question here is whether you need tasking,
> >or whether a minimal runtime system, of the kind that would
> >typically be used in a safety-critical system, would be
> >usable. One approach that some of our customers are exploring
> >is the use of our GNORT (GNAT No Run-Time) technology that
> >provides a subset of Ada which generates absolutely ZERO
> >bytes of runtime. This means that you can simply generate
> >object files and then run them to the bare board using
> >whatever low level toolset is appropriate.
> >
> >One customer for example is using OS/2 as the development
> >environment, and then GNORT for actual delivery to the
> >target system (which is a bare board x86).
> >
>     I'm curious about GNORT. Does the "zero bytes of runtime" mean
>     that there are no compiler supplied procedures or functions that
>     are ever called to do some common task? By which, I mean something
>     like common code that does a bounds check and raises an exception,
>     or something similar. I do  not mean something like the standard
>     libraries for math functions, etc. (Those you can possibly treat
>     as regular packages as if you wrote them yourself, provided you
>     have enough information about the actual implementation) All the
>     code for whatever statements are compiled is generated as some
>     in-line machine code?
>
>     If you were to allow for subroutines for common operations like
>     bounds checking, would there be any difference in providing
>     subroutines for more complex features, such as task scheduling?
>     (Other than the possible non-determinism. I'm thinking that a
>     run-time library is not necessarily evil if it results in smaller
>     code by sharing some frequently repeated operations and the
>     tradeoff between procedure call overhead and space savings is
>     reasonable.)
>
>     Just curious about how this stuff is done...
>
>     MDC

Right, there are NO runtime routines of any kind. All code
is generated inline. No one is saying that a run-time library
is evil, the problem is that in a certified environment you
have to use a certified run-time.

Not only is it expensive to certify a run-time, an expense
that is inevitably passed on to the user, but in any case it
is preferable to not have to rely on some separate
certification procedure, but instead to certify all your
own code, and have that be the only code that needs
certifying.

GNORT is certainly not for everyone, it is specifically
intended for meeting the needs for safety critical
certified code at a relatively modest cost, compared to
the use of certified run-times.

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