GCC and out-of-range constant array indexes?

[Basile Starynkevitch]

On Fri, 08 Oct 2010 11:03:27 -0700
Ian Lance Taylor <iant@google.com> wrote:

> Basile Starynkevitch <basile@starynkevitch.net> writes:
> 
> > Howeer, I see a logic in needing -O2 to get some warnings.
> > Optimizations are expensive, and they compute static properties of the
> > source code, which are usable (& necessary and used) for additional
> > warnings.
> 
> The problem that I think we've discovered over the years is that when
> warnings depend on optimizations, the warnings are unstable.  It means
> that as optimizations change, the warnings appear and disappear.  And
> that means that as people move their code to new compiler releases, they
> get unpredictable new warnings.

Is this unstability of warnings related to the (perhaps stupid)
folklore of avoiding -O3 (what I mean is that, for instance, most Linux
distributions are built with -O2 at most; very few are using -O3; this
brings a chicken & egg issue: since -O3 is much less used, it is
probably more buggy & less usable!).

But I also noticed (even on the runtime inside the MELT branch of GCC)
that newer GCC releases give better & more warnings than older ones.

(BTW, Ian, I am still hoping for your review & ok of my gengtype patches!).

Cheers.

-- 
Basile STARYNKEVITCH         http://starynkevitch.net/Basile/
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