GNU bug report logs - #21844
`sort` behavior unstable based on neighboring elements ?

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Mike Frysinger <vapier <at> gentoo.org>
To: bug-coreutils <at> gnu.org
Subject: `sort` behavior unstable based on neighboring elements ?
Date: Fri, 6 Nov 2015 11:41:41 -0500

[Message part 1 (text/plain, inline)]

i got this bug report today about sort mismatches.  the order of the
inputs changes the order of the outputs which surprised me.  but it
might be a nuance of unicode collation i'm not familiar with ?

$ printf '%s\n' aarch64 abc zed | LC_ALL=nb_NO.UTF-8 sort -u
aarch64
abc
zed
$ printf '%s\n' abc aarch64 zed | LC_ALL=nb_NO.UTF-8 sort -u
abc
zed
aarch64

why aren't the outputs here the same ?  a nordic user pointed out
that aa is an alternative for å which comes after z, which is fine,
but that doesn't explain why the output isn't the same here.
-mike

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Message #8 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Pádraig Brady <P <at> draigBrady.com>
To: bug-coreutils <at> gnu.org, Mike Frysinger <vapier <at> gentoo.org>
Subject: Re: bug#21844: `sort` behavior unstable based on neighboring elements
 ?
Date: Fri, 6 Nov 2015 16:53:02 +0000

tag 21844 notabug
close 21844
stop

On 06/11/15 16:41, Mike Frysinger wrote:
> i got this bug report today about sort mismatches.  the order of the
> inputs changes the order of the outputs which surprised me.  but it
> might be a nuance of unicode collation i'm not familiar with ?
> 
> $ printf '%s\n' aarch64 abc zed | LC_ALL=nb_NO.UTF-8 sort -u
> aarch64
> abc
> zed
> $ printf '%s\n' abc aarch64 zed | LC_ALL=nb_NO.UTF-8 sort -u
> abc
> zed
> aarch64
> 
> why aren't the outputs here the same ?  a nordic user pointed out
> that aa is an alternative for å which comes after z, which is fine,
> but that doesn't explain why the output isn't the same here.
> -mike

strcoll is giving the wrong results:

$ printf '%s\n' abc aarch64 zed | LC_ALL=nb_NO.UTF-8 ltrace -e strcoll sort >/dev/null
sort->strcoll("aarch64", "zed")                                                = 3
sort->strcoll("abc", "zed")                                                    = -25

$ printf '%s\n' aarch64 abc zed | LC_ALL=nb_NO.UTF-8 ltrace -e strcoll sort >/dev/null
sort->strcoll("abc", "zed")                                                    = -25
sort->strcoll("aarch64", "abc")                                                = -1

I think this is due to:
https://sourceware.org/bugzilla/show_bug.cgi?id=18589

Fixed by:
https://sourceware.org/git/?p=glibc.git;a=commit;h=87701a58

cheers,
Pádraig.

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