[Linux-kernel-mentees] [PATCH] checkpatch: fix false positive for REPEATED_WORD warning

[Lukas Bulwahn]

On Wed, 21 Oct 2020, Dwaipayan Ray wrote:

> Hey Aditya and Lukas,
> 
> > > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > > > index 9b9ffd876e8a..181c95691715 100755
> > > > --- a/scripts/checkpatch.pl
> > > > +++ b/scripts/checkpatch.pl
> > > > @@ -3052,7 +3052,9 @@ sub process {
> > > >
> > > >  # check for repeated words separated by a single space
> > > >             if ($rawline =~ /^\+/ || $in_commit_log) {
> > > > -                   while ($rawline =~ /\b($word_pattern) (?=($word_pattern))/g) {
> > > > +                   # avoid repeating hex occurrences like 'ff ff fe 09 ...'
> > > > +                   while ($rawline !~ /((\s)*[0-9a-z]{2}( )+){4,}/ &&
> 
> Pattern is probably wrong. It doesn't recognize word boundaries or
> tabs between words. Example of the first type:
> 
> 000 00 ff ff ...
>

I am wondering if this pattern really appears.

Hex stuff is usually written two-letter and spaces.

Maybe it is best to limit it to 0-9a-f, though. I think there should not 
be matches with other letters than that.

Aditya, evaluations on those alternatives would help to make decisions.

> The regex matches "00 00 ff ff" ignoring the first 0.
>
> I think it could be perhaps better with something like:
> 
>  # check for repeated words separated by a single space
> -               if ($rawline =~ /^\+/ || $in_commit_log) {
> +               if (($rawline =~ /^\+/ || $in_commit_log) &&
> +                   $rawline !~ /(?:\b(?:[0-9a-f]{2}\s+){4,})/) {
>                         pos($rawline) = 1 if (!$in_commit_log);
>                         while ($rawline =~ /\b($word_pattern)
> (?=($word_pattern))/g) {
> 
> Please test it though. I only ran it on a few patterns.
> 
> Apart from it, this does fix the problem. But I am quite sceptical about
> matching 4 or more 2 lettered words in a row. There could be counter
> examples but I guess that is very rare. It's not very general, but for
> the moment it does the job.
> 
> So I think it's probably good with some changes. Not sure what Joe
> would have in mind though.
> 
> Lukas, I think with the changes in place, it is ready to go for discussion.
>

Dwaipayan, thanks for your review.

Lukas