n3294 - The restrict function attribute as a replacement of the restrict qualifier

[Alejandro Colomar]

Hi Branden!

On Fri, Jul 26, 2024 at 11:35:51AM GMT, G. Branden Robinson wrote:
> At 2024-07-26T16:24:14+0000, Joseph Myers wrote:
> > I know that "noalias" was included in some C89 drafts but removed from
> > the final standard after objections.  Maybe someone who was around
> > then could explain what "noalias" was, what the problems with it were
> 
> For this part, I think the source most often cited is Dennis Ritchie's
> thunderbolt aimed directly at "noalias".
> 
> https://www.lysator.liu.se/c/dmr-on-noalias.html

Thanks!  It seems Dennis's concern was that it was a qualifier.
Probably the reason why restrict ended up being a qualifier on the
pointer (and thus easily ignored), instead of the pointee (it would have
caused the problems that Dennis mentioned and which anyone can guess).

Since I'm suggesting an attribute, we are pretty much safe from type
rules, and thus safe from Dennis's concerns, I think.

Have a lovely night!
Alex

> 
> > and how it differs from "restrict",
> 
> I can only disqualify myself as an authority here.
> 
> > To comprehensively address this demands so we can make sure that any
> > new proposals in this area don't suffer from whatever the perceived
> > deficiencies of "noalias" were?
> 
> I think it would be valuable to get such a discussion into the rationale
> of the next C standard.
> 
> Regards,
> Branden

-- 
<https://www.alejandro-colomar.es/>
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