GNU bug report logs - #25336

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

From: Zepp Lu <luzepu678 <at> gmail.com>
To: bug-grep <at> gnu.org
Date: Mon, 2 Jan 2017 21:22:59 +0800

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OS: Archlinux
grep version: 2.27-1

Bug description: grep behaves weirdly when searching hex values.

How to reproduce:
$ printf '\x53\xef' | grep -aoP '\x53\xef'
(no output, returns 1)
$ printf '\x53\xc3\xaf' | grep -aoP '\x53\xef'
Sï
$ printf '\x53\xc3\xef' | grep -aoP '\x53\xef'
(no output, returns 1)

grep (version 2.12-2) provided by Debian works just fine.

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Message #10 received at 25336-done <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Zepp Lu <luzepu678 <at> gmail.com>, 25336-done <at> debbugs.gnu.org
Subject: Re: bug#25336:
Date: Mon, 2 Jan 2017 10:30:32 -0800

Zepp Lu wrote:

> $ printf '\x53\xef' | grep -aoP '\x53\xef'
> (no output, returns 1)
> $ printf '\x53\xc3\xaf' | grep -aoP '\x53\xef'
> Sï
> $ printf '\x53\xc3\xef' | grep -aoP '\x53\xef'
> (no output, returns 1)

I don't see a bug here. PCRE patterns like \xef match code points, not bytes, so 
the PCRE notation differs from the shell printf notation. If your locale uses 
UTF-8, the PCRE pattern \xef matches the Unicode character U+00EF LATIN SMALL 
LETTER I WITH DIAERESIS, which is represented by the byte pair C3 AF.

If you want \xef to match a single byte, run grep in a single-byte locale, e.g., 
set LC_ALL=C in the environment.

> grep (version 2.12-2) provided by Debian works just fine.

Actually, it's buggy in this area. Sometimes it can dump core.

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