Re: Array out of bounds warning

[Geoff Keating <geoffk at cygnus dot com>]

Kamil Iskra <kamil@wins.uva.nl> writes:

> On Mon, 31 Jul 2000, Jeffrey A Law wrote:
> 
> >   > int a[10];
> >   > a[10] = 17;
> [snip]
> > The next question in my mind is how often do we get false hits on the
> > warning.
> 
> I've been wondering: what will the proposed patch do for n-dimensional
> arrays, say:
> 
> int a[10][10];
> a[0][10]=17;
> 
> I think right now the code will generate a warning, but is this what we
> want?
> 
> I'm not entirely sure whether the standard does allow such a construction,
> but surely it has a well defined meaning, given that the memory layout of
> arrays is precisely defined in the standard. I've seen such a code only
> yesterday, where it was used for speed reasons, so it's probably not an
> uncommon trick.

The behaviour is rendered undefined by the ISO C standard.  This is
precisely so that compilers can do bounds-checking on references like
these.

-- 
- Geoffrey Keating <geoffk@cygnus.com>