Commit 70eb2275 authored by Dwaipayan Ray's avatar Dwaipayan Ray Committed by Linus Torvalds
Browse files

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

Modifiers %h and %hh should never be used.

Commit cbacb5ab ("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.camel@perches.com/
Link: https://lkml.kernel.org/r/20201128200046.78739-1-dwaipayanray1@gmail.com


Signed-off-by: default avatarDwaipayan Ray <dwaipayanray1@gmail.com>
Suggested-by: default avatarJoe Perches <joe@perches.com>
Suggested-by: default avatarLukas Bulwahn <lukas.bulwahn@gmail.com>
Acked-by: default avatarJoe Perches <joe@perches.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 831242ab

scripts/checkpatch.pl

+22 −0
Original line number Diff line number Diff line
@@ -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*>>/ &&