From: Xi Ruoyao <xry111@xry111.site>
To: Adhemerval Zanella Netto <adhemerval.zanella@linaro.org>,
Vincent Lefevre <vincent@vinc17.net>,
Turritopsis Dohrnii Teo En Ming <teo.en.ming@protonmail.com>,
"libc-alpha@sourceware.org" <libc-alpha@sourceware.org>,
"ceo@teo-en-ming-corp.com" <ceo@teo-en-ming-corp.com>
Subject: Re: New GNU C Library (glibc) security flaw reported on 30 Jan 2024
Date: Thu, 01 Feb 2024 02:47:18 +0800 [thread overview]
Message-ID: <96521764f4636c9ea3f3089f369975c12fa8be77.camel@xry111.site> (raw)
In-Reply-To: <c622583d-a7f5-45ad-8195-0d8238469823@linaro.org>
On Wed, 2024-01-31 at 12:52 -0300, Adhemerval Zanella Netto wrote:
/* snip */
>
> I see this is an manual issue rather than a GNU 'extension' to qsort semantic.
> And I think we should fix BZ#31322 by using a transitive comparison instead of
> trying to support such cases.
To me the documentation is correct (though arguably in a very subtle
way):
Here is an example of a comparison function which works with an array
of numbers of type ‘double’:
int
compare_doubles (const void *a, const void *b)
{
const double *da = (const double *) a;
const double *db = (const double *) b;
return (*da > *db) - (*da < *db);
}
It says "numbers." But NaN literally means, "Not a Number." C23 says:
Floating types shall be able to represent signed zeros or an unsigned
zero and all normalized floating-point numbers. In addition, floating
types may be able to contain other kinds of floating-point numbers, such
as subnormal floating-point numbers and unnormalized floating-point
numbers, and values that are not floating-point numbers, such as NaNs
and (signed and unsigned) infinities. A NaN is a value signifying Not-
a-Number.
So at least in C23 it's clear that NaN and infinite values are not
numbers.
--
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University
next prev parent reply other threads:[~2024-01-31 18:47 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-01-31 14:08 Turritopsis Dohrnii Teo En Ming
2024-01-31 14:23 ` Xi Ruoyao
2024-01-31 14:55 ` Vincent Lefevre
2024-01-31 15:52 ` Adhemerval Zanella Netto
2024-01-31 16:23 ` Vincent Lefevre
2024-01-31 16:44 ` Siddhesh Poyarekar
2024-01-31 18:47 ` Xi Ruoyao [this message]
2024-02-01 0:51 ` Vincent Lefevre
2024-02-01 1:03 ` Vincent Lefevre
2024-02-01 6:41 ` Xi Ruoyao
2024-02-01 9:07 ` Vincent Lefevre
2024-02-01 19:55 ` Paul Eggert
2024-02-01 21:11 ` Siddhesh Poyarekar
2024-02-05 0:58 ` Paul Eggert
2024-02-06 15:00 ` Zack Weinberg
2024-02-06 21:30 ` Paul Eggert
2024-02-06 22:04 ` Xi Ruoyao
2024-02-07 17:07 ` Zack Weinberg
2024-02-07 19:55 ` Alexander Monakov
2024-02-07 20:45 ` Zack Weinberg
2024-02-07 21:53 ` Alexander Monakov
2024-02-07 22:56 ` Paul Eggert
2024-04-06 17:17 ` Paul Eggert
2024-04-08 8:28 ` Florian Weimer
2024-04-22 14:39 ` Zack Weinberg
2024-04-23 18:09 ` Paul Eggert
2024-04-23 18:26 ` Florian Weimer
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