Date: Mon, 11 Aug 2003 07:30:59 +0200
From: Willy Tarreau <willy@w.ods.org>
To: Chip Salzenberg <chip@pobox.com>
Cc: Jamie Lokier <jamie@shareable.org>,
       Albert Cahalan <albert@users.sourceforge.net>,
       linux-kernel mailing list <linux-kernel@vger.kernel.org>,
       davem@redhat.com
Subject: Re: [PATCH] 2.4.22pre10: {,un}likely_p() macros for pointers
Message-ID: <20030811053059.GB28640@alpha.home.local>
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On Sun, Aug 10, 2003 at 10:39:12PM -0400, Chip Salzenberg wrote:
 
> Both parameters of __builtin_expect() are long ints.  On an
> architecture where there's a pointer type larger than long[1],
> __builtin_expect() won't just warn, it'll *fail*.  Also, on an
> architecture where a conversion of a null pointer to long results in
> a non-zero value[2], it'll *fail*.  That makes it non-portable twice
> over.  Wouldn't you agree?

Hmmm Chip, on the document you suggested us to read, I remember a statement
about (!x) <=> (x == 0) which implied it's legal even if x is a pointer because
the compiler will automatically do the comparison between x and NULL and not
(int)x and 0. Perhaps I have dreamed, but I'm sure I read this. So in any case,
the !!(x) construct should be valid.

Cheers,
Willy

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