bisect_perl_using_git - Man Page

bisect_perl_using_git helps you to bisect Perl. This helps you to find at what commit a change happened in Perl. You can check for file addition and removal - it checks out various commits of Perl and finds out which change was involved. You can also check for a difference in Perl evalutation, in which case it will check out various commits of Perl, compile them and finds out which change was involved - this is more CPU intensive and you must install ccache.

First you must download the current Git repository of Perl, so execute something like the following:

  mkdir git
  cd git
  git clone git://perl5.git.perl.org/perl.git perl-git
  cd perl-git

Now, I happen to know that the autodie pragma was added sometime in December 2008, but I would like to know which commit. Let's find out some commits at the beginning and the end of that month, and see when lib/autodie.pm was added:

  # git log --before=2008-12-01 -n 1
  # 1409bc0658469580630ba458c85fe9cc3cb2d78c
  # git log --before=2008-12-31 -n 1
  # 675b0f774d374f6951c02c6463c64a746ad46acd
  git bisect reset
  git bisect start
  git bisect good 1409bc0658469580630ba458c85fe9cc3cb2d78c
  git bisect bad 675b0f774d374f6951c02c6463c64a746ad46acd
  # Bisecting: 114 revisions left to test after this
  git bisect run bisect_perl_using_git --action file_added \
    --filename lib/autodie.pm
  # ... after checking out 10 trees and about 10 seconds, it says:
  # 0b09a93a0cec34bc5d1740400c4ed9500d2f1dbe is first bad commit
  # commit 0b09a93a0cec34bc5d1740400c4ed9500d2f1dbe
  # Author: Paul Fenwick <pjf@perltraining.com.au>
  # Date:   Sat Dec 20 22:21:02 2008 +0900
  #
  # git-flavoured autodie 1.997 patch
  # G'day p5p,
  # ...
  git bisect reset

Sometime after June 2009, ext/Storable/MANIFEST was removed from Perl. Let's find out which commit removed it:

  # git log --before=2009-06-01 -n 1
  # 20f91e418dfa8bdf6cf78614bfebebc28a7613ee
  git bisect reset
  git bisect start
  git bisect good 20f91e418dfa8bdf6cf78614bfebebc28a7613ee
  git bisect bad HEAD
  # Bisecting: 266 revisions left to test after this
  git bisect run bisect_perl_using_git --action file_removed \
    --filename ext/Storable/MANIFEST
  # ... after checking out 11 trees and about 10 seconds, it says:
  # 2868e48536e3f471e5ba483466cc1bc53caff5a is first bad commit
  # commit e2868e48536e3f471e5ba483466cc1bc53caff5a
  # Author: David Mitchell <davem@iabyn.com>
  # Date:   Fri Jun 12 17:24:43 2009 +0100
  #
  #    remove ext/Storable/MANIFEST; its out of date related to CPAN
  #    and for most dual-life modules we don't bother including it in blead
  # ...
  git bisect reset

Now for a real bug report, where some code that works in Perl 5.8.8 and should work in Perl 5.10.0 but does not:

  http://rt.perl.org/rt3/Public/Bug/Display.html?id=62056

We create a ~/testcase.pl which contains the following:

  #!perl
  use strict;
  use warnings;
  use charnames ':full';
  my $x;
  m/$x\N{START OF HEADING}/

And then run:

  git bisect reset
  git bisect start
  git bisect good perl-5.8.8
  git bisect bad perl-5.10.0
  # Bisecting: 4041 revisions left to test after this
  git bisect run bisect_perl_using_git --action perl_fails \
    --filename ~/testcase.pl
  # ... after checking out 16 trees and about one hour, it says:
  # fc8cd66c26827f6c2ee1aa00ab2d3b3c320a4a28 is first bad commit
  # commit fc8cd66c26827f6c2ee1aa00ab2d3b3c320a4a28
  # Author: Yves Orton <demerphq@gmail.com>
  # Date:   Tue Sep 19 03:37:19 2006 +0200
  #
  #    Re: \N{...} in regular expression [PATCH]
  # ...
  git bisect reset

Leon Brocard, <acme@astray.com>

Copyright (C) 2009, Leon Brocard

This module is free software; you can redistribute it or modify it under the same terms as Perl itself.