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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Certified C compilers for safety-critical embedded systems
Date: 17 Jan 2004 15:50:16 -0500
Organization: The World Public Access UNIX, Brookline, MA
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"Robert I. Eachus" <rieachus@comcast.net> writes:

> Having said that, there are tests in the ACATS suite, that AFAIK, have
> never been successfully compiled by any compiler.  But they are still
> believed to be legal Ada programs.  (Mostly floating point programs that
> require types with digits from 15 to 30.  Again, AFIAK some of these
> correctly compile on VAXes and on IBM mainframes, but no one has yet
> supported digits 30.)

I think a better way to look at it is: "legality" is somewhat defined by
the compiler.  Ada compilers are not required to support "digits 30" --
so if you write such a program, it is simply illegal (for most
compilers).  And Ada compilers can detect that just fine.  Nothing to do
with Godel or Halting Problems.

Ada compilers can also detect when they are given programs that exceed
the compiler's capacity (memory to store the parse tree, for example).
Such programs are simply illegal (for that compiler).

- Bob