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Re: [perl #133948] Blead breaks CPAN: 2abbd513b8 breaks MP3::Tag

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From:
James E Keenan
Date:
March 22, 2019 22:35
Subject:
Re: [perl #133948] Blead breaks CPAN: 2abbd513b8 breaks MP3::Tag
Message ID:
20190322223532.10334.qmail@lists-nntp.develooper.com
On 3/22/19 5:02 PM, Karl Williamson wrote:
> On 3/22/19 11:51 AM, James E Keenan (via RT) wrote:
>> # New Ticket Created by  James E Keenan
>> # Please include the string:  [perl #133948]
>> # in the subject line of all future correspondence about this issue.
>> # <URL: https://rt.perl.org/Ticket/Display.html?id=133948 >
>>
>>
>> As reported to the perl5-porters newsgroup earlier today, I noticed test
>> failures in MP3-Tag when building it as part of the CPAN-River-3000 run
>> kicked off yesterday after the release of perl-5.29.9.  Since I was not
>> immediately certain that the fault lay in blead, and since this module
>> is throwing a lot of "deprecated in perl-5.32" warnings, I began by
>> simply opening this bug ticket:
>>
>> https://rt.cpan.org/Ticket/Display.html?id=128915
>>
>> The module proved difficult to bisect because its build process requires
>> the user to respond to prompts.
>>
>> Eventually, with the following bisection command:
>>
>> #####
>> perl Porting/bisect.pl -Uuseithreads --start=v5.29.8 --end=v5.29.9
>> --module=MP3::Tag
>> #####
>>
>> ... I was able to identify a problematic commit:
>>
>> #####
>> HEAD is now at 2abbd513b8 Implement variable length lookbehind in regex
>> patterns
>> bad - non-zero exit from /tmp/YJl89Q_BUW/bin/perl -I /home/jkeenan/.cpan
>> -MCPAN::MyConfig -MCPAN -e
>> $CPAN::Config->{build_dir}=q{/tmp/hAZueFfERu}; -e install('MP3::Tag');
>> die unless CPAN::Shell->expand(Module => 'MP3::Tag')->uptodate;
>> 2abbd513b87245ddb806e6bc4f59945ecb46dced is the first bad commit
>> commit 2abbd513b87245ddb806e6bc4f59945ecb46dced
>> Author: Karl Williamson <khw@cpan.org>
>> Date:   Sun Mar 17 21:06:10 2019 -0600
>>
>>       Implement variable length lookbehind in regex patterns
>>
>>       See [perl #132367].
>>
> 
> This should be fixed by
> 
> commit 39ce401c1db32fe69d69d11cfd7b62071e52f43a
>   Author: Karl Williamson <khw@cpan.org>
>   Date:   Fri Mar 22 14:54:33 2019 -0600
> 
>       PATCH: [perl #133984] Failure in lookbehind
> 
>       I thought that lookbehind assertions weren't supposed to look 
> beyond the
>       current position; but this CPAN module demonstrates that they can 
> look
>       ahead as well.
> 
>       I built some infrastructure to prevent them from looking ahead.  In
>       part, this is because Unicode recommends that pattern matching 
> have the
>       ability to restrict the area of the target being matched.  That
>       infrastructure is not needed at this time.  But I think we should 
> leave
>       it in for now anyway, as we see what other bugs the variable length
>       lookbehind changes may have caused.
> 
>       So this patch just takes the easy way out, and at the place where it
>       would restrict the area searched, it uses the full width.  It's a one
>       line change.

Looks good to me.

#####
[blead] $ ./bin/perl -Ilib -V:config_args
config_args='-des -Dusedevel -Uversiononly 
-Dprefix=/home/jkeenan/testing/blead -Dman1dir=none -Dman3dir=none 
-Duseithreads -Doptimize=-O2 -pipe -fstack-protector -fno-strict-aliasing';

[blead] $ ./bin/cpanm MP3::Tag
--> Working on MP3::Tag
Fetching 
http://www.cpan.org/authors/id/I/IL/ILYAZ/modules/MP3-Tag-1.14.tar.gz ... OK
Configuring MP3-Tag-1.14 ... OK
Building and testing MP3-Tag-1.14 ... OK
Successfully installed MP3-Tag-1.14
1 distribution installed
#####

But we should leave this RT open for a while to see what other breakage 
occurs.

Thank you very much.
Jim Keenan

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