[debbugs-tracker] bug#16865: closed (grep -wP and backreferences)

[GNU bug Tracking System]

Your message dated Tue, 25 Feb 2014 10:03:28 -0800
with message-id <address@hidden>
and subject line Re: bug#16865: grep -wP and backreferences
has caused the debbugs.gnu.org bug report #16865,
regarding grep -wP and backreferences
to be marked as done.

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16865: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=16865
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> --- Begin Message ---
>
>
>
> Subject: 
>
> grep -wP and backreferences
>
>
>
>
> Date: 
>
> Mon, 24 Feb 2014 10:01:54 +0000
>
>
>
>
> User-agent: 
>
> Mutt/1.5.21 (2010-09-15)
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>
>
>
> Hello,
>
> Backreferences don't work with -w or -x in combination with -P:
>
> $ echo aa | grep -Pw '(.)\1'
> $
>
> Or they work in an unexpected way:
>
> $ echo aa | grep -Pw '(.)\2'
> aa
>
> The fix is simple:
>
>
> --- src/pcresearch.c~   2014-02-24 09:59:56.864374362 +0000
> +++ src/pcresearch.c    2014-02-24 07:33:04.666398105 +0000
> @@ -75,9 +75,9 @@ Pcompile (char const *pattern, size_t si
>  
>    *n = '\0';
>    if (match_lines)
> -    strcpy (n, "^(");
> +    strcpy (n, "^(?:");
>    if (match_words)
> -    strcpy (n, "\\b(");
> +    strcpy (n, "\\b(?:");
>    n += strlen (n);
>  
>    /* The PCRE interface doesn't allow NUL bytes in the pattern, so
>
>
>
> --- End Message ---

--- Begin Message --- Subject: Re: bug#16865: grep -wP and backreferences Date: Tue, 25 Feb 2014 10:03:28 -0800

On Tue, Feb 25, 2014 at 8:08 AM, Stephane Chazelas
<address@hidden> wrote:
> 2014-02-24 20:55:42 -0800, Jim Meyering:
>> On Mon, Feb 24, 2014 at 1:20 PM, Stephane Chazelas
>> <address@hidden> wrote:
>> > A last note: with -w, pcregrep wraps the regexp in \b...\b
>> > instead of \b(?:...)\b, so it could be that those brackets are
>> > not necessary in the first place.
>
> The brackets are actually needed in cases like:
>
> grep -Pw 'foo|bar'
>
> (pcregrep has a bug there).
>
>
>> > Maybe instead of \b(?:...)\b, we could use (?<!\w)...(?!\w)
>> >
>> > $ echo a%%b | grep -P '(?<!\w)%%(?!\w)'
>> > $ echo %aa% | grep -P '(?<!\w)aa(?!\w)'
>> > %aa%
>>
>> I like both suggestions. Making -wP work like grep's -w makes perfect sense.
>> Care to prepare a patch to make it do that, with a separate test case?
>> "git format-patch ..." output preferred, if you're game.
>>
>> I pushed the above patch, but would welcome another one.
>
> Please find the patch attached.

Thank you very much.  Nearly perfect.
I've uncapitalized the 1-line summary, changed a That to This
in the log, and added examples to NEWS, and added an empty
line to restore the 2-empty-line section delimiter.

> (note that tests/word-delim-multibyte fails for me, but it's not
> my doing, it was failing before).

That's an XFAIL test (as noted in tests/Makefile.am), hence, expected
to fail, and as long as it fails as expected, "make check" can still succeed.

I've closed this ticket, and will push once you ack these changes.

0001-align-grep-Pw-with-grep-w.patch
Description: Binary data

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