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From:   David Laight <David.Laight@ACULAB.COM>
To:     'Rasmus Villemoes' <linux@rasmusvillemoes.dk>,
        Kees Cook <keescook@chromium.org>,
        Jonathan Corbet <corbet@lwn.net>
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        Martin Uecker <Martin.Uecker@med.uni-goettingen.de>,
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        Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>,
        Rikard Falkeborn <rikard.falkeborn@gmail.com>,
        Arnd Bergmann <arnd@arndb.de>,
        "linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
        Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-hardening@vger.kernel.org" <linux-hardening@vger.kernel.org>
Subject: RE: [PATCH] linux/const.h: Explain how __is_constexpr() works
Thread-Topic: [PATCH] linux/const.h: Explain how __is_constexpr() works
Thread-Index: AQHYF2x1W+MAhayA/keZ5Xju46h+qqx/89kw
Date:   Wed, 2 Feb 2022 08:49:33 +0000
Message-ID: <8e166131c01b4fbc83a1ca95b83bc362@AcuMS.aculab.com>
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 <dc86fdf7-3202-e836-6f71-af1e2458b105@rasmusvillemoes.dk>
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From: Rasmus Villemoes
> Sent: 01 February 2022 13:06
...
> > + * - The C standard defines an "integer constant expression" as different
> > + *   from a "null pointer constant" (an integer constant 0 pointer).
> 
> I don't see the point of this bullet. Yes, an ICE is a distinct concept
> from a null pointer constant, obviously. One is defined in terms of the
> other - and your parenthesis is not an accurate paraphrase of the
> definition of a null pointer constant.

From what I remember a "null pointer constant" is in "integer constant
expression with value 0 cast to a pointer type".
So (void *)(1-1) is just as valid as (void *)0.

Not sure any of it is relevant here.

	David

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