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From: "Jeff C," <nolongersafeto@userealemailsniff.com>
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Subject: Re: Certified C compilers for safety-critical embedded systems
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"James Rogers" <jimmaureenrogers@att.net> wrote in message
news:Xns945DE49836882jimmaureenrogers@204.127.36.1...
> Robert A Duff <bobduff@shell01.TheWorld.com> wrote in
> news:wccekur4151.fsf@shell01.TheWorld.com:
>
> > Chris Hills <chris@phaedsys.org> writes:
> >> So it all has to be enforced by the compiler?
> >
> > No, it doesn't.  I agree with you that (in principle) there's nothing
> > wrong with running 'lint' or whatever in addition to the compiler.
> > However, 'lint' (in the case of C) doesn't have enough information
> > to perform the checks that are routinely done by Ada compilers.
>
> Two simple examples are array bounds checking and scalar range checking.
>
> The C standard explicitly permits accessing one element beyond the end
> of an array. Neither the C compiler nor lint can determine if an array
> index is outside the bounds of the array. Ada compilers detect static
> references beyond the end of an array every time.
>
> Examples:
>
> int foo[10];
>
> int i;
>
> for(i = 0; i < 100; ++i)
> {
>    foo[i] = i;
> }
>
> Although human inspection clearly identifies the for loop indices
> to be beyond the bounds of the array, neither the C compiler nor lint
> will detect the problem. Since the problem can be clearly identified



While most C compilers and lint won't find this, there are static analysis
tools that can. Granted the
tools may be able to do a better job on Ada code because there is more
information to work with but
simple cases like you presented here (even if the loop was "far away:" from
foo) can be detected
by tools like Programming Research QA C (No Ada Available) and Polyspace
(Ada available)..

Perhaps even by the LDRA static analysis tools (Ada available) though I have
less to go on for this tool.