GNU bug report logs - #44352
Incorrect matches for some ERE

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

From: Gonzalo Padrino <grimalgon <at> gmail.com>
To: bug-grep <at> gnu.org
Subject: Incorrect matches for some ERE
Date: Sat, 31 Oct 2020 16:26:25 +0100

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

  While using GNU grep v3.4 in an Ubuntu 20.04 userspace running on top of
Win10 WSL (yeah, i know... but also checked in other envs) i discovered
what seems like an obvious bug (if i'm not mistaken).

  The bug:
-----
me <at> host:~$  echo 'xxxxy' |grep -E '^x+x+x+x+y$'
xxxxy
me <at> host:~$  echo 'xxxy' |grep -E '^x+x+x+x+y$'
xxxy
me <at> host:~$  echo 'xxy' |grep -E '^x+x+x+x+y$'
xxy
me <at> host:~$  echo 'xy' |grep -E '^x+x+x+x+y$'

----
...the terminal supports ansi color escapes, and what's really weird is
that only the result from the first command is colored in red. First and
fourth commands yield correct results; the second and third do not, as they
should not match it's input.

  I've tested releases from v3.1 to latest v3.5 and found the anomalous
behaviour in version v3.2 through v3.5. A (quick and clunky) git bisect led
me to believe it was introduced about two years ago, possibly in commit
123620af88f55c3e0cc9f0aed7311c72f625bc82 (
https://git.savannah.gnu.org/cgit/grep.git/commit/?id=123620af88f55c3e0cc9f0aed7311c72f625bc82
).
If this is true, it would mean either the bug is in gnulib, or maybe grep
needed to do some kind of extra handling on it's side.

Kind regards. Gonzalo Padrino.

P.S.: I had to patch some things in order to successfully compile the code
after checking out some problematic commits (pragmas to avoid warnings
about "pure" and "noreturn" function attributes, a missing configmake
dependency in bootstrap.conf, etc ).

P.S.: Resending message since first got lost in aether apparently.

[Message part 2 (text/html, inline)]

Message #10 received at 44352 <at> debbugs.gnu.org (full text, mbox):

From: Jim Meyering <jim <at> meyering.net>
To: Gonzalo Padrino <grimalgon <at> gmail.com>
Cc: 44352 <at> debbugs.gnu.org
Subject: Re: bug#44352: Incorrect matches for some ERE
Date: Sat, 31 Oct 2020 11:51:29 -0700

On Sat, Oct 31, 2020 at 9:18 AM Gonzalo Padrino <grimalgon <at> gmail.com> wrote:
>   While using GNU grep v3.4 in an Ubuntu 20.04 userspace running on top of
> Win10 WSL (yeah, i know... but also checked in other envs) i discovered
> what seems like an obvious bug (if i'm not mistaken).
>
>   The bug:
> -----
> me <at> host:~$  echo 'xxxxy' |grep -E '^x+x+x+x+y$'
> xxxxy
> me <at> host:~$  echo 'xxxy' |grep -E '^x+x+x+x+y$'
> xxxy
> me <at> host:~$  echo 'xxy' |grep -E '^x+x+x+x+y$'
> xxy
> me <at> host:~$  echo 'xy' |grep -E '^x+x+x+x+y$'
>
> ----
> ...the terminal supports ansi color escapes, and what's really weird is
> that only the result from the first command is colored in red. First and
> fourth commands yield correct results; the second and third do not, as they
> should not match it's input.
>
>   I've tested releases from v3.1 to latest v3.5 and found the anomalous
> behaviour in version v3.2 through v3.5. A (quick and clunky) git bisect led
> me to believe it was introduced about two years ago, possibly in commit
> 123620af88f55c3e0cc9f0aed7311c72f625bc82 (
> https://git.savannah.gnu.org/cgit/grep.git/commit/?id=123620af88f55c3e0cc9f0aed7311c72f625bc82
> ).
> If this is true, it would mean either the bug is in gnulib, or maybe grep
> needed to do some kind of extra handling on it's side.
>
> Kind regards. Gonzalo Padrino.
>
> P.S.: I had to patch some things in order to successfully compile the code
> after checking out some problematic commits (pragmas to avoid warnings
> about "pure" and "noreturn" function attributes, a missing configmake
> dependency in bootstrap.conf, etc ).
>
> P.S.: Resending message since first got lost in aether apparently.

Thanks. It was not lost. Conversation is continuing on
https://bugs.gnu.org/44351

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