From: enh <enh@google.com>
To: Zack Weinberg <zack@owlfolio.org>
Cc: Ralf Jung <post@ralfj.de>,
Wilco Dijkstra <Wilco.Dijkstra@arm.com>,
GNU libc development <libc-alpha@sourceware.org>
Subject: Re: Support for memcpy with equal source and destination
Date: Mon, 27 Nov 2023 07:02:26 -0800 [thread overview]
Message-ID: <CAJgzZoof0fp=3L3e+Av2rPXh_rkAM=WNwznRyg=ms2nJ4n+j2w@mail.gmail.com> (raw)
In-Reply-To: <b1096608-56e5-46a9-b40b-c793a71e87ff@app.fastmail.com>
On Mon, Nov 27, 2023 at 6:54 AM Zack Weinberg <zack@owlfolio.org> wrote:
>
> On Mon, Nov 27, 2023, at 9:45 AM, Ralf Jung wrote:
> >> Paul's example was to show that with restrict you could write a conformant
> >> C implementation. I think it is sufficient to cast away restrict without adding an
> >> extra branch (the existing generic C version does this).
> >
> > I don't think it is possible to cast away restrict. The restrict rules apply to
> > all pointers derived from the restrict pointer.
>
> As a practical matter, if we remove restrict annotations from the public memcpy
> declaration in string.h, _someone_ is going to think that's a bug, and also I
> wouldn't be surprised if future compilers started complaining about mismatches
> with their internal prototype. (Neither GCC 13 nor clang 16 does this _now_.)
fwiw, bionic doesn't use `restrict` at all in headers, and no human or
compiler has noticed yet.
> zw
next prev parent reply other threads:[~2023-11-27 15:02 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-27 14:38 Wilco Dijkstra
2023-11-27 14:45 ` Ralf Jung
2023-11-27 14:53 ` Zack Weinberg
2023-11-27 15:02 ` enh [this message]
-- strict thread matches above, loose matches on Subject: below --
2023-11-27 19:28 Aaron Peter Bachmann
2023-11-27 19:39 ` Paul Eggert
2023-11-23 12:14 Adhemerval Zanella Netto
2023-11-25 7:48 ` Paul Eggert
2023-11-25 8:20 ` Ralf Jung
2023-11-25 17:11 ` Paul Eggert
2023-11-27 11:15 ` Ralf Jung
2023-11-27 11:46 ` Alexander Monakov
2023-11-27 12:34 ` Ralf Jung
2023-11-27 14:25 ` Alexander Monakov
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