Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail
From: Keith Thompson <Keith.S.Thompson+u@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: Baby X is bor nagain
Date: Thu, 20 Jun 2024 13:37:29 -0700
Organization: None to speak of
Lines: 26
Message-ID: <874j9nxsdy.fsf@nosuchdomain.example.com>
References: <v494f9$von8$1@dont-email.me> <v4c8s4$1lki1$4@dont-email.me>
	<20240613002933.000075c5@yahoo.com> <v4emki$28d1b$1@dont-email.me>
	<20240613174354.00005498@yahoo.com> <v4okn9$flpo$2@dont-email.me>
	<20240617002924.597@kylheku.com> <v4pddb$m5th$1@dont-email.me>
	<20240618115650.00006e3f@yahoo.com> <v4rv0o$1b7h1$1@dont-email.me>
	<20240618184026.000046e1@yahoo.com> <v4sd75$1ed31$1@dont-email.me>
	<877celzx14.fsf@nosuchdomain.example.com>
	<v4u85k$1t2pu$2@dont-email.me> <v4ucmn$1u14i$1@dont-email.me>
	<v4v2br$22c0m$1@dont-email.me> <v4v5nu$230rh$2@dont-email.me>
	<v4vfrn$24rv6$1@dont-email.me> <v50n9s$2fkko$1@dont-email.me>
	<v50poh$2g4ha$1@dont-email.me> <87iky3svqh.fsf@bsb.me.uk>
MIME-Version: 1.0
Content-Type: text/plain
Injection-Date: Thu, 20 Jun 2024 22:37:30 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="b9721cdd33060f6c797cf39cb31eeba2";
	logging-data="2883838"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19eTG5uiQPImdP7nIb4HN4n"
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux)
Cancel-Lock: sha1:27sVXm1MrjMZ0zU1hmQUbBgURgA=
	sha1:BZLCegqQ2Kkb+JMMOUSiLVS1nag=
Bytes: 2634

Ben Bacarisse <ben@bsb.me.uk> writes:
[...]
> On a C language point, I don't think the standard says anything about
> sorting with non-order functions like the one above.  Is an
> implementation of qsort permitted to misbehave (for example by not
> terminating) when the comparison function does not implement a proper
> order relation?

N1570 7.22.5p4 (applies to bsearch and qsort):
"""
When the same objects (consisting of size bytes, irrespective of
their current positions in the array) are passed more than once to
the comparison function, the results shall be consistent with one
another. That is, for qsort they shall define a total ordering on
the array, and for bsearch the same object shall always compare
the same way with the key.
"""

That's a "shall" outside a constraint, so violating it results in
undefined behavior.

N3220 7.24.5 has the same wording.

-- 
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */