From: "Uecker, Martin" <Martin.Uecker@med.uni-goettingen.de>
To: "keescook@chromium.org" <keescook@chromium.org>,
"linux@rasmusvillemoes.dk" <linux@rasmusvillemoes.dk>,
"corbet@lwn.net" <corbet@lwn.net>,
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Subject: Re: [PATCH] linux/const.h: Explain how __is_constexpr() works
Date: Wed, 2 Feb 2022 15:43:02 +0000 [thread overview]
Message-ID: <4eb192f15c9078984c5e05a9fdc85ab6a9611717.camel@med.uni-goettingen.de> (raw)
In-Reply-To: <8e166131c01b4fbc83a1ca95b83bc362@AcuMS.aculab.com>
Am Mittwoch, den 02.02.2022, 08:49 +0000 schrieb David Laight:
> 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.
The C standard (at least public drafts essentially
identical to the actual standards) can be found here:
http://www.open-std.org/jtc1/sc22/wg14/www/projects#9899
"An integer constant expression with the value 0, or such
an expression cast to type void *, is called a null pointer
constant."
BTW: I think it would be very valuable if WG14 would get
proposals and/or comments from the kernel community.
Martin
> David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
>
next prev parent reply other threads:[~2022-02-02 15:43 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-31 20:43 [PATCH] linux/const.h: Explain how __is_constexpr() works Kees Cook
2022-01-31 21:26 ` Gustavo A. R. Silva
2022-02-01 12:01 ` Jani Nikula
2022-02-01 13:05 ` Rasmus Villemoes
2022-02-01 15:09 ` Matthew Wilcox
2022-02-02 8:49 ` David Laight
2022-02-02 15:43 ` Uecker, Martin [this message]
2022-02-02 20:14 ` Miguel Ojeda
2022-02-02 16:19 ` David Laight
2022-02-02 20:13 ` Miguel Ojeda
2022-02-02 22:20 ` David Laight
2022-02-02 23:01 ` Miguel Ojeda
2022-02-02 23:08 ` Nick Desaulniers
2022-02-02 20:44 ` Rasmus Villemoes
2022-02-02 22:42 ` David Laight
2022-02-03 0:28 ` Miguel Ojeda
2022-02-02 20:43 ` Miguel Ojeda
2022-02-03 9:25 ` David Laight
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