From: Richard Biener <richard.guenther@gmail.com>
To: Joseph Myers <joseph@codesourcery.com>
Cc: libc-coord@lists.openwall.com, GCC Development <gcc@gcc.gnu.org>,
GNU C Library <libc-alpha@sourceware.org>
Subject: Re: [libc-coord] Add new ABI '__memcmpeq()' to libc
Date: Fri, 17 Sep 2021 09:43:55 +0200 [thread overview]
Message-ID: <CAFiYyc0nghZMYdhO9T2h92oOZtnxTHUikhgw46Gp9mme5_nVvA@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2109162033510.2510762@digraph.polyomino.org.uk>
On Thu, Sep 16, 2021 at 10:36 PM Joseph Myers <joseph@codesourcery.com> wrote:
>
> On Thu, 16 Sep 2021, Chris Kennelly wrote:
>
> > In terms of relying on the feature: If __memcmpeq is ever exposed as an a
> > simple alias for memcmp (since the notes mention that it's a valid
> > implementation), does that open up the possibility of depending on the
> > bcmp-like behavior that we were trying to escape?
>
> The proposal is as an ABI only (compilers would generate calls to
> __memcmpeq from boolean uses of memcmp, users wouldn't write calls to
> __memcmpeq directly, __memcmpeq wouldn't be declared in installed libc
> headers). If such dependence arises, that would suggest a compiler bug
> wrongly generating such calls for non-boolean memcmp uses.
So the compiler would emit a call to __memcmpeq and at the same time
emit a weak alias of __memcmpeq to memcmp so the program links
when the libc version targeted does not provide __memcmpeq? Or would
glibc through <string.h> magically communicate the availability of the new ABI
without actually declaring the function?
(I'm not sure whether a GCC build-time decision via configure is the
very best idea)
Richard.
> --
> Joseph S. Myers
> joseph@codesourcery.com
next prev parent reply other threads:[~2021-09-17 7:44 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-16 17:02 Noah Goldstein
2021-09-16 17:55 ` [libc-coord] " Chris Kennelly
2021-09-16 18:31 ` Noah Goldstein
2021-09-16 20:32 ` Chris Kennelly
2021-09-16 20:35 ` Joseph Myers
2021-09-16 20:55 ` enh
2021-09-17 7:43 ` Richard Biener [this message]
2021-09-17 8:08 ` Florian Weimer
2021-09-17 8:31 ` Richard Biener
2021-09-17 8:37 ` Florian Weimer
2021-09-17 9:30 ` Richard Biener
2021-09-17 17:40 ` Noah Goldstein
2021-09-17 9:12 ` Jakub Jelinek
2021-09-17 16:55 ` Martin Sebor
2021-09-17 14:19 ` Joseph Myers
2021-09-17 14:26 ` Florian Weimer
2021-09-21 19:53 ` Noah Goldstein
2021-09-22 17:46 ` Christoph Müllner
2021-09-22 18:15 ` Noah Goldstein
2021-09-16 21:27 ` James Y Knight
2021-09-16 21:42 ` Joseph Myers
2021-09-16 21:50 ` enh
2021-09-16 21:59 ` Noah Goldstein
2021-09-16 22:17 ` Chris Kennelly
2021-09-16 22:36 ` Joseph Myers
2021-09-16 23:24 ` Noah Goldstein
2021-09-18 1:36 ` James Y Knight
2021-10-26 22:47 ` Noah Goldstein
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