On Thu, 2020-11-26 at 14:16 +0530, Dwaipayan Ray 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.
>
> Link:
> https://lore.kernel.org/lkml/[email protected]/
>
> Suggested-by: Lukas Bulwahn <[email protected]>
> Signed-off-by: Dwaipayan Ray <[email protected]>
> ---
> Changes in v2:
> - Use $logFunctions instead of the manual list.
> - Relocate the check to after logging continuations check.
> - Remove perl_version_ok condition which is unneeded here.
[]
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -6027,6 +6027,18 @@ sub process {
> "Avoid logging continuation uses where feasible\n"
> . $herecurr);
> }
>
> +# check for unnecessary use of %h[xudi] and %hh[xudi] in logging functions
> + if (defined $stat &&
> + $line =~ /\b$logFunctions\s*\(/) {
> + 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 modifiers %h[xudi] or
> %hh[xudi]\n" . "$here\n$stat_real\n");
o Why not capture the group and show the actual integer format portion here?
(%[\d\.\*\-]*h+[idux])
o This might also show every unnecessary use of %h. (using while (.../g)
o The .*\" isn't useful.
o The /i is probably wrong.
o Perhaps this could use a --fix line if the format is on the same line
as $logFunctions
o Perhaps the message should say something about integer promotion.
Maybe something like:
"Integer promotion: using 'h' in '$1' is unnecessary\n"
