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Message-ID: <alpine.DEB.2.22.394.2109162033510.2510762@digraph.polyomino.org.uk>
Date: Thu, 16 Sep 2021 20:35:39 +0000
From: Joseph Myers <joseph@...esourcery.com>
To: <libc-coord@...ts.openwall.com>
CC: Noah Goldstein <goldstein.w.n@...il.com>, <gcc@....gnu.org>, GNU C Library
	<libc-alpha@...rceware.org>
Subject: Re: Add new ABI '__memcmpeq()' to libc

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.

-- 
Joseph S. Myers
joseph@...esourcery.com

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