bug#28846: Maybe a bug in "sort (GNU coreutils) 8.4" report

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Dear coreutils :
I am a Research and Development Engineer in IT. I met a situation when I
use “sort” command in Linux shell which could be a bug for the "sort"
command. So I hope you read this email, thank you !

The whole command I used was ：
*sort test.txt*

*And the result was :*
20171012|3|2059517|-|8|-|20-24|2|-|2.0|2.0
20171012|3|2059517|-|82|-|25-29|2|-|13.0|12.0
20171012|3|2059517|-|8|-|-2|-2|-|71.0|64.0
20171012|3|2059517|-|82|-|30-34|0|-|2.0|1.0

*The content in test.txt was:*
20171012|3|2059517|-|8|-|20-24|2|-|2.0|2.0
20171012|3|2059517|-|82|-|25-29|2|-|13.0|12.0
20171012|3|2059517|-|8|-|-2|-2|-|71.0|64.0
20171012|3|2059517|-|82|-|30-34|0|-|2.0|1.0

*Which means the “sort” command didn't work, because I think the correct
result should be :*
20171012|3|2059517|-|8|-|20-24|2|-|2.0|2.0
20171012|3|2059517|-|8|-|20-24|2|-|2.0|2.0
20171012|3|2059517|-|82|-|25-29|2|-|13.0|12.0
20171012|3|2059517|-|82|-|25-29|2|-|13.0|12.0

*The version of "sort" command I use is : sort --version*
"sort (GNU coreutils) 8.4
Copyright (C) 2010 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html
>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Mike Haertel and Paul Eggert."

*I am not sure if it is a bug in "sort" command in Linux Shell or maybe
it's only my problems in using it.*
*So I am look forward to receive your reply as soon as possible. *
*Thank you very much!*

Sincerely yours,

Frank