From: Jakub Jelinek <jakub@redhat.com>
To: Richard Biener <richard.guenther@gmail.com>
Cc: "Uecker, Martin" <Martin.Uecker@med.uni-goettingen.de>,
"Peter.Sewell@cl.cam.ac.uk" <Peter.Sewell@cl.cam.ac.uk>,
"gcc@gcc.gnu.org" <gcc@gcc.gnu.org>,
"law@redhat.com" <law@redhat.com>,
"cl-c-memory-object-model@lists.cam.ac.uk"
<cl-c-memory-object-model@lists.cam.ac.uk>
Subject: Re: C provenance semantics proposal
Date: Thu, 18 Apr 2019 12:47:00 -0000 [thread overview]
Message-ID: <20190418124717.GB21066@tucnak> (raw)
In-Reply-To: <CAFiYyc26TDZ-JZT8ufxEUMp0UXOym8mno3d7cdJ+6B7QajCMsw@mail.gmail.com>
On Thu, Apr 18, 2019 at 02:42:22PM +0200, Richard Biener wrote:
> > 1.) Compilers do not use conditional equivalences for
> > optimizations of pointers (or only when additional
> > conditions apply which make it safe)
> >
> > 2.) We make pointer comparison between a pointer
> > and a one-after pointer of a different object
> > undefined behaviour.
>
> Yes please! OTOH GCC transforms
> (uintptr_t)&a != (uintptr_t)(&b+1)
> into &a != &b + 1 (for equality compares) and then
I think we don't. It was http://gcc.gnu.org/PR88775, but we haven't applied
those changes, because we don't consider the point to start of one object
vs. pointer to end of another one case in pointer comparisons (but do
consider it in integral comparisons).
Jakub
next prev parent reply other threads:[~2019-04-18 12:47 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-02 8:11 Peter Sewell
2019-04-12 14:51 ` Jeff Law
2019-04-12 15:31 ` Peter Sewell
2019-04-17 9:06 ` Richard Biener
2019-04-17 9:15 ` Peter Sewell
2019-04-17 9:41 ` Richard Biener
2019-04-17 11:53 ` Uecker, Martin
2019-04-17 12:41 ` Richard Biener
2019-04-17 12:56 ` Uecker, Martin
2019-04-17 13:35 ` Richard Biener
2019-04-17 14:12 ` Uecker, Martin
2019-04-17 17:31 ` Peter Sewell
2019-04-18 9:32 ` Richard Biener
2019-04-18 9:56 ` Richard Biener
2019-04-18 10:48 ` Peter Sewell
2019-04-18 11:57 ` Uecker, Martin
2019-04-18 12:31 ` Richard Biener
2019-04-18 13:25 ` Uecker, Martin
2019-04-18 10:45 ` Peter Sewell
2019-04-18 12:20 ` Uecker, Martin
2019-04-18 12:42 ` Richard Biener
2019-04-18 12:47 ` Jakub Jelinek [this message]
2019-04-18 12:51 ` Jakub Jelinek
2019-04-18 13:29 ` Jeff Law
2019-04-24 10:12 ` Richard Biener
2019-04-18 13:49 ` Uecker, Martin
2019-04-19 8:19 ` Jens Gustedt
2019-04-19 8:49 ` Jakub Jelinek
2019-04-19 9:09 ` Jens Gustedt
2019-04-19 9:34 ` Jakub Jelinek
2019-04-21 8:15 ` Jens Gustedt
2019-04-24 10:24 ` Richard Biener
2019-04-24 18:43 ` Jeff Law
2019-04-24 19:21 ` Jens Gustedt
2019-04-19 9:11 ` Peter Sewell
2019-04-19 9:15 ` Jens Gustedt
2019-04-19 9:35 ` Peter Sewell
2019-04-19 10:35 ` Uecker, Martin
2019-04-19 10:01 ` Uecker, Martin
2019-04-18 13:42 ` Jeff Law
2019-04-18 13:54 ` Uecker, Martin
2019-04-18 14:49 ` Peter Sewell
2019-04-18 15:09 ` Uecker, Martin
2019-04-24 10:19 ` Richard Biener
2019-04-24 18:41 ` Jeff Law
2019-04-24 19:30 ` Philipp Klaus Krause
2019-04-24 19:55 ` Uecker, Martin
2019-04-24 19:33 ` Jakub Jelinek
2019-04-24 21:19 ` Peter Sewell
2019-04-25 12:42 ` Richard Biener
2019-04-25 13:03 ` Peter Sewell
2019-04-25 13:13 ` Richard Biener
2019-04-25 13:20 ` Peter Sewell
2019-04-29 14:31 ` Joseph Myers
2019-04-25 12:39 ` Richard Biener
2019-05-09 11:26 ` Ralf Jung
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