Re: [Linux-kernel-mentees] [PATCH] checkpatch: Fix the usage of capture group ( ... )

[Lukas Bulwahn <lukas.bulwahn@gmail.com>]

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On Sun, Jul 12, 2020 at 2:20 PM Mrinal Pandey <mrinalmni@gmail.com> wrote:

> On 20/07/12 09:18AM, Lukas Bulwahn wrote:
> > On Sun, Jul 12, 2020 at 7:18 AM Mrinal Pandey <mrinalmni@gmail.com>
> wrote:
> >
> > > On Sun, Jul 12, 2020 at 12:44 AM Lukas Bulwahn <
> lukas.bulwahn@gmail.com>
> > > wrote:
> > >
> > >>
> > >>
> > >> On Sat, Jul 11, 2020 at 5:44 PM Mrinal Pandey <mrinalmni@gmail.com>
> > >> wrote:
> > >>
> > >>> The usage of "capture group (...)" in the immediate condition after
> `&&`
> > >>> results in `$1` being uninitialized. This eventually crashes the
> script.
> > >>>
> > >>>
> > >> It does not really crash it, right? It just emits a warning.
> > >>
> > >
> > > Sir,
> > >
> > > Yes. I will modify the line accordingly.
> > >
> > >>
> > >>
> > >>> Fix this by placing the capture group in the condition before `&&`.
> > >>> Thus, `$1` can be initialized to the text it matches thereby setting
> it
> > >>> to the desired and required value.
> > >>>
> > >>>
> > >> Maybe you can look when this bug was introduced?
> > >>
> > >
> > > The bug was first introduced with the commit `e518e9a59ec3` when the
> block
> > > was
> > > added to the script. It has been like that since then.
> > > Should I add this detail too in the commit message?
> > >
> >
> > Yes, please do.
> >
> > Commits are referred to with its hash shortened to 12 characters and the
> > commit message header in the following format:
> >
> > Commit e518e9a59ec3 ("checkpatch: emit an error when there's a diff in a
> > changelog")
> >
> >
> > Further note:
> > - can you also explain what the author intended to do?
> > - can you describe in one sentence how you discovered this bug?
> > - use checkpatch.pl on your own patch.
> >
> > Please rework the commit message and resend to this list, Shuah and me.
> >
> > I think if that patch is then okay, we have a quick look and then you can
> > send it out to the general list.
> >
> Sir,
>
> Please let me know if the commit message could be further improved or
> this is what you seek.
> I ran my patch through checkpatch and it says that the patch has no
> obvious style problems.
> I hope I wasn't supposed to include patch version history on this patch,
> please correct me if I am wrong.
>
> Thank you.
> >
> > Lukas
> >
> > >
>
> The usage of "capture group (...)" in the immediate condition after `&&`
> results in `$1` being uninitialized. This issues a warning "Use of
> uninitialized value $1 in regexp compilation at ./scripts/checkpatch.pl
> line 2638".
>
> I noticed this bug while running checkpatch on the set of commits from
> v5.7 to v5.8-rc1 of the kernel. The warning was thrown on the commits
> which had a diff content in their commit message.
>
>  Just drop " . The warning was thrown" and say:

  I noticed this bug while running checkpatch on the set of commits from
v5.7 to v5.8-rc1 of the kernel on the commits with a diff content in their
commit message.

> This bug was introduced in the script by Commit e518e9a59ec3
> ("checkpatch: emit an error when there's a diff in a changelog"). It has
> been in the script since then.
>
>
s/Commit/commit


> The author intended to store the match made by capture group in variable
> `$1`. This should have contained the name of the file as `[\w/]+` matched.
> However, this couldn't be accomplished due to usage of capture group and
> `$1` in the same RegEx.
>
>
s/RegEx/regular expression/


> Fix this by placing the capture group in the condition before `&&`.
> Thus, `$1` can be initialized to the text which capture group matches
> thereby setting it to the desired and required value.
>
> s/which/that/


Fix those minor points and send the patch to lkml and the maintainers (CC:
me, Shuah, and the list).

Read through the instructions for sending patches and follow all the
guidelines.

Lukas

Signed-off-by: Mrinal Pandey <mrinalmni@gmail.com>
> ---
>  scripts/checkpatch.pl | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 4c820607540b..e73e998d582a 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -2636,8 +2636,8 @@ sub process {
>
>  # Check if the commit log has what seems like a diff which can confuse
> patch
>                 if ($in_commit_log && !$commit_log_has_diff &&
> -                   (($line =~ m@^\s+diff\b.*a/[\w/]+@ &&
> -                     $line =~ m@^\s+diff\b.*a/([\w/]+)\s+b/$1\b@) ||
> +                   (($line =~ m@^\s+diff\b.*a/([\w/]+)@ &&
> +                     $line =~ m@^\s+diff\b.*a/[\w/]+\s+b/$1\b@) ||
>                      $line =~ m@^\s*(?:\-\-\-\s+a/|\+\+\+\s+b/)@ ||
>                      $line =~ m/^\s*\@\@ \-\d+,\d+ \+\d+,\d+ \@\@/)) {
>                         ERROR("DIFF_IN_COMMIT_MSG",
> --
> 2.25.1
>
>

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