Re: [PATCH v3] checkpatch: add new exception to repeated word check

[Joe Perches]

On Sat, 2020-10-17 at 10:52 +0530, Dwaipayan Ray wrote:
> Recently, commit 4f6ad8aa1eac ("checkpatch: move repeated word test")
> moved the repeated word test to check for more file types. But after
> this, if checkpatch.pl is run on MAINTAINERS, it generates several
> new warnings of the type:
> 
> WARNING: Possible repeated word: 'git'
> 
> For example:
> WARNING: Possible repeated word: 'git'
> +T:	git git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml.git
> 
> So, the pattern "git git://..." is a false positive in this case.
> 
> There are several other combinations which may produce a wrong
> warning message, such as "@size size", ":Begin begin", etc.
> 
> Extend repeated word check to compare the characters before and
> after the word matches. If the preceding or succeeding character
> belongs to the exception list, the warning is avoided.
> 
> Link: https://lore.kernel.org/linux-kernel-mentees/81b6a0bb2c7b9256361573f7a13201ebcd4876f1.camel@xxxxxxxxxxx/
> Suggested-by: Joe Perches <joe@xxxxxxxxxxx>
> Suggested-by: Lukas Bulwahn <lukas.bulwahn@xxxxxxxxx>
> Signed-off-by: Dwaipayan Ray <dwaipayanray1@xxxxxxxxx>
> ---
>  scripts/checkpatch.pl | 17 +++++++++++++++--
>  1 file changed, 15 insertions(+), 2 deletions(-)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index f1a4e61917eb..89430dfd6652 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -595,6 +595,7 @@ our @mode_permission_funcs = (
>  );
>  
>  my $word_pattern = '\b[A-Z]?[a-z]{2,}\b';
> +my $exclude_chars = '[^\.\,\+\s]';

Why include a + character here?

>  #Create a search pattern for all these functions to speed up a loop below
>  our $mode_perms_search = "";
> @@ -3056,15 +3057,27 @@ sub process {
>  
>  				my $first = $1;
>  				my $second = $2;
> -
> +				my $start_pos = $-[1];
> +				my $end_pos = $+[2];
>  				if ($first =~ /(?:struct|union|enum)/) {
>  					pos($rawline) += length($first) + length($second) + 1;
>  					next;
>  				}
>  
> -				next if ($first ne $second);
> +				next if (lc($first) ne lc($second));
>  				next if ($first eq 'long');
>  
> +				# check for character before and after the word matches
> +				my $start_char = '';
> +				my $end_char = '';
> +				$start_char = substr($rawline, $start_pos - 1, 1) if ($start_pos > 0);
> +				$end_char = substr($rawline, $end_pos, 1) if ($end_pos <= length($rawline));


substr uses index 0, so I believe the if should be < 

> +
> +				if ($start_char =~ /^$exclude_chars$/ ||
> +				    $end_char =~ /^$exclude_chars$/) {
> +					next;
> +				}
 
Please use "next if (test);" to be similar to the other uses above.

And this doesn't work on end of phrase or sentence.

ie: "my sentence is is, a duplicate word word."

so $end_char could be a comma or a period.

so likely the $end_char test should be !~

What is the reason to add and use $exclude_chars?