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

Modifiers %h and %hh should never be used.

Commit cbacb5ab0a ("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: Dwaipayan Ray <dwaipayanray1@gmail.com>
Suggested-by: Joe Perches <joe@perches.com>
Suggested-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Acked-by: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Dwaipayan Ray 2020-12-15 20:45:15 -08:00 committed by Linus Torvalds
parent 831242ab8d
commit 70eb2275ff
1 changed files with 22 additions and 0 deletions
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22
scripts/checkpatch.pl
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@ -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*>>/ &&