linux-kernel - Re: [PATCH v4] checkpatch: fix false positives in REPEATED

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Date:   Fri, 23 Oct 2020 18:37:16 -0700
From:   Joe Perches <joe@...ches.com>
To:     Aditya Srivastava <yashsri421@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        lukas.bulwahn@...il.com, dwaipayanray1@...il.com
Subject: Re: [PATCH v4] checkpatch: fix false positives in REPEATED_WORD
 warning

On Sat, 2020-10-24 at 05:38 +0530, Aditya Srivastava wrote:
> Presence of hexadecimal address or symbol results in false warning
> message by checkpatch.pl.
> 
> For example, running checkpatch on commit b8ad540dd4e4 ("mptcp: fix
> memory leak in mptcp_subflow_create_socket()") results in warning:
> 
> WARNING:REPEATED_WORD: Possible repeated word: 'ff'
>     00 00 00 00 00 00 00 00 00 2f 30 0a 81 88 ff ff  ........./0.....
> 
> Similarly, the presence of list command output in commit results in
> an unnecessary warning.
> 
> For example, running checkpatch on commit 899e5ffbf246 ("perf record:
> Introduce --switch-output-event") gives:
> 
> WARNING:REPEATED_WORD: Possible repeated word: 'root'
>   dr-xr-x---. 12 root root    4096 Apr 27 17:46 ..
> 
> Here, it reports 'ff' and 'root to be repeated, but it is in fact part

'root'

> of some address or code, where it has to be repeated.
> 
> In these cases, the intent of the warning to find stylistic issues in
> commit messages is not met and the warning is just completely wrong in
> this case.
> 
> To avoid these warnings, add additional regex check for the

add an

> directory permission pattern and avoid checking the line for this
> class of warning. Similarly, to avoid hex pattern, check if the word
> consists of hex symbols and skip this warning if it is not among the
> common english words formed using hex letters.
> 
> A quick evaluation on v5.6..v5.8 showed that this fix reduces
> REPEATED_WORD warnings from 2797 to 907.

How many of these 907 remaining are still false positive?
 
> A quick manual check found all cases are related to hex output or
> list command outputs in commit messages.

You mean 1890 of the 2797 are now no longer reported and all 1890
were false positives yes?

> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -3049,7 +3049,9 @@ sub process {
>  		}
>  
> 
>  # check for repeated words separated by a single space
> -		if ($rawline =~ /^\+/ || $in_commit_log) {
> +# avoid false positive from list command eg, '-rw-r--r-- 1 root root'
> +		if (($rawline =~ /^\+/ || $in_commit_log) &&
> +                    $rawline !~ /[bcCdDlMnpPs\?-][rwxsStT-]{9}/) {

Use maximal tab indentation and spaces to align please.
2 tabs, 4 spaces

>  			pos($rawline) = 1 if (!$in_commit_log);
>  			while ($rawline =~ /\b($word_pattern) (?=($word_pattern))/g) {
>  
> 
> @@ -3074,6 +3076,17 @@ sub process {
>  				next if ($start_char =~ /^\S$/);
>  				next if (index(" \t.,;?!", $end_char) == -1);
>  
> 
> +                                # avoid repeating hex occurrences like 'ff ff fe 09 ...'
> +                                my %allow_repeated_words = (
> +                                        add => '',
> +                                        added => '',
> +                                        bad => '',
> +                                        be => '',
> +                                );

If perl caches this local hash declaration, fine,
but I think it better to use 'our %allow_repeated_words'
and move it so it's only declared using the file scope.

> +                                if ($first =~ /\b[0-9a-f]{2,}\b/) {

This regex matches only lower case so it wouldn't match "Add".

I think this regex would be clearer using
	/^[0-9a-f]+$/i or /^[A-Fa-f0-9]+$/