[Linux-kernel-mentees] [PATCH RFC] checkpatch: add warning for unnecessary use of %h[xudi] and %hh[xudi]

Lukas Bulwahn lukas.bulwahn at gmail.com
Wed Nov 25 19:34:33 UTC 2020


On Mi., 25. Nov. 2020 at 20:05, Dwaipayan Ray <dwaipayanray1 at gmail.com>
wrote:

> Modifiers %h and %hh should never be used.
>
> Commit cbacb5ab0aa0 ("docs: printk-formats: Stop encouraging use
> of unnecessary %h[xudi] and %hh[xudi]") specifies that:
>
> "Standard integer promotion is already done and %hx and %hhx is useless
> so do not encourage the use of %hh[xudi] or %h[xudi]."
>
> "The "h" and "hh" things should never be used. The only reason for them
> being used if you have an "int", but you want to print it out as a
> "char" (and honestly, that is a really bad reason, you'd be better off
> just using a proper cast to make the code more obvious)."
>
> Add a new check to emit a warning on finding an unneeded use of %h or
> %hh modifier.
>

Looks good. You might want to add the link to the original email discussion
on lore.kernel.org in the commit message with Link:

Lukas


> Suggested-by: Lukas Bulwahn <lukas.bulwahn at gmail.com>
> Signed-off-by: Dwaipayan Ray <dwaipayanray1 at gmail.com>
> ---
>  scripts/checkpatch.pl | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 7dc094445d83..47c1017a9973 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -6570,6 +6570,19 @@ sub process {
>                         }
>                 }
>
> +# check for unnecessary use of %h[xudi] and %hh[xudi]
> +               if ($perl_version_ok &&
> +                   defined $stat &&
> +                   $line =~
> /(?:[sd]?print[kfd]|(?:pr_|drm_)(?:info|debug|warn|error))/i) {
> +                       my $lc = $stat =~ tr@\n@@;
> +                       $lc = $lc + $linenr;
> +                       my $stat_real = get_stat_real($linenr, $lc);
> +                       if ($stat_real =~
> /\"[^\"]*%[\d\.\*\-]*h+[idux].*\"/i) {
> +                               WARN("UNNECESSARY_MODIFIER",
> +                                    "Unnecessary use of length modifiers
> %h[xudi] or %hh[xudi]\n" . "$here\n$stat_real\n");
> +                       }
> +               }
> +
>  # check for naked sscanf
>                 if ($perl_version_ok &&
>                     defined $stat &&
> --
> 2.27.0
>
>
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