linux-kernel - Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL" test

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Message-ID: <CAOh2x=mpUY4MN2U065azTbY_cH1bO0j_=i4QApXtoC5J+zEc6A@mail.gmail.com>
Date:	Thu, 27 Aug 2015 07:49:42 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Joe Perches <joe@...ches.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Dan Carpenter <dan.carpenter@...cle.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Mike Holmes <mike.holmes@...aro.org>, nmorey@...ray.eu
Subject: Re: [PATCH] checkpatch: add --strict "pointer comparison to NULL" test

On Fri, Nov 14, 2014 at 12:27 AM, Joe Perches <joe@...ches.com> wrote:
> It seems there are more and more uses of "if (!ptr)"
> in preference to "if (ptr == NULL)" so add a --strict
> test to emit a message when using the latter form.
>
> This also finds (ptr != NULL).
>
> Fix it too if desired.
>
> Signed-off-by: Joe Perches <joe@...ches.com>
> ---
> Seeing no objections, so submitting it.
>
>  scripts/checkpatch.pl | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
>
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 24d6702..d4e08bc 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -4490,6 +4490,20 @@ sub process {
>                              "Possible precedence defect with mask then right shift - may need parentheses\n" . $herecurr);
>                 }
>
> +# check for pointer comparisons to NULL
> +               if ($^V && $^V ge 5.10.0) {
> +                       while ($line =~ /\b$LvalOrFunc\s*(==|\!=)\s*NULL\b/g) {
> +                               my $val = $1;
> +                               my $equal = "!";
> +                               $equal = "" if ($4 eq "!=");
> +                               if (CHK("COMPARISON_TO_NULL",
> +                                       "Comparison to NULL could be written \"${equal}${val}\"\n" . $herecurr) &&
> +                                           $fix) {
> +                                       $fixed[$fixlinenr] =~ s/\b\Q$val\E\s*(?:==|\!=)\s*NULL\b/$equal$val/;
> +                               }
> +                       }
> +               }
> +

Hi Joe,

Sorry for picking a relatively old thread.

Few colleagues asked me why isn't checkpatch warning for (NULL == ptr)
or (NULL != ptr) checks, as it warns for (ptr == NULL) and (ptr != NULL).

Did you miss it? or was it intentional ?

--
viresh
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