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.
Also add a fix option to the check.
Link:
https://lore.kernel.org/lkml/4910042649a4f3ab22fac93191b8c1fa0a2e17c3.ca...@perches.com/
Suggested-by: Joe Perches <j...@perches.com>
Suggested-by: Lukas Bulwahn <lukas.bulw...@gmail.com>
Signed-off-by: Dwaipayan Ray <dwaipayanr...@gmail.com>
---
Changes in v4:
- Change warning type and message
- Use $stat_real and calculate line offset during matches
- fix option now works for any patch line
- # was added to format block to match %#06hh
Changes in v3:
- Change warning message
- Fix regex match to include capture group
- Warn on every unnecesary use of %h on a line
- Add fix option when the format line matches current line
Changes in v2:
- Use $logFunctions instead of the manual list.
- Relocate the check to after logging continuations check.
- Remove perl_version_ok check
scripts/checkpatch.pl | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 7dc094445d83..3c86ea737e9c 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -6027,6 +6027,28 @@ 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*\(/ &&
+ index($stat, '"') >= 0) {
+ my $lc = $stat =~ tr@\n@@;
+ $lc = $lc + $linenr;
+ my $stat_real = get_stat_real($linenr, $lc);
+ pos($stat_real) = index($stat_real, '"');
+ while ($stat_real =~
/[^\"%]*(%[\#\d\.\*\-]*(h+)[idux])/g) {
+ my $pspec = $1;
+ my $h = $2;
+ my $lineoff = substr($stat_real, 0, $-[1]) =~
tr@\n@@;
+ if (WARN("UNNECESSARY_MODIFIER",
+ "Integer promotion: Using '$h' in
'$pspec' is unnecessary\n" . "$here\n$stat_real\n") &&
+ $fix && $fixed[$fixlinenr + $lineoff] =~
/^\+/) {
+ my $nspec = $pspec;
+ $nspec =~ s/h//g;
+ $fixed[$fixlinenr + $lineoff] =~
s/\Q$pspec\E/$nspec/;
+ }
+ }
+ }
+
# check for mask then right shift without a parentheses
if ($perl_version_ok &&
$line =~ /$LvalOrFunc\s*\&\s*($LvalOrFunc)\s*>>/ &&
--
2.27.0
