C provenance semantics proposal

[Peter Sewell]

On Thu, 18 Apr 2019 at 14:54, Uecker, Martin
<Martin.Uecker@med.uni-goettingen.de> wrote:
>
> Am Donnerstag, den 18.04.2019, 07:42 -0600 schrieb Jeff Law:
> > On 4/18/19 6:20 AM, Uecker, Martin wrote:
> > > Am Donnerstag, den 18.04.2019, 11:45 +0100 schrieb Peter Sewell:
> > > > On Thu, 18 Apr 2019 at 10:32, Richard Biener <richard.guenther@gmail.com> wrote:
>
> ...
> > > 4.) Compilers make sure that exposed objects never
> > > are allocated next to each other (as Jens proposed).
> >
> > Ugh.  Not sure how you enforce that.  Consider that the compiler may
> > ultimately have no control over layout of data in static storage.
>
> One maybe only where it matters? I assume the biggest benefit
> is for local variables and there the compiler has full control.
>
> For arbitrary pointer coming from somewhere, one has no provenance
> information anyway.

that's not quite true - one does know that it can't have the same provenance
as anything created more recently than the incoming pointer

> Best,
> Martin