[54/95] checkpatch: add warning for unnecessary use of %h[xudi] and %hh[xudi]

Commit Message

Andrew Morton Dec. 16, 2020, 4:45 a.m. UTC

From: Dwaipayan Ray <[e-mail]>
Subject: checkpatch: add warning for unnecessary use of %h[xudi] and %hh[xudi]

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/[e-mail]/
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Dwaipayan Ray <[e-mail]>
Suggested-by: Joe Perches <[e-mail]>
Suggested-by: Lukas Bulwahn <[e-mail]>
Acked-by: Joe Perches <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 scripts/checkpatch.pl |   22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

Patch

--- a/scripts/checkpatch.pl~checkpatch-add-warning-for-unnecessary-use-of-%h-and-%hh
+++ a/scripts/checkpatch.pl
@@ -6102,6 +6102,28 @@  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*>>/ &&