Commit abb08a53 authored by Joe Perches's avatar Joe Perches Committed by Linus Torvalds
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checkpatch: try to avoid mask and shift errors

Shift has a higher precedence that mask so warn when a mask then shift
operation is done without parentheses around the mask.

This test works well for a right shift, but the left shift is pretty
commonly done correctly so only warn on the right shift.
Signed-off-by: default avatarJoe Perches <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 36061e38
......@@ -4482,6 +4482,14 @@ sub process {
# check for mask then right shift without a parentheses
if ($^V && $^V ge 5.10.0 &&
$line =~ /$LvalOrFunc\s*\&\s*($LvalOrFunc)\s*>>/ &&
$4 !~ /^\&/) { # $LvalOrFunc may be &foo, ignore if so
"Possible precedence defect with mask then right shift - may need parentheses\n" . $herecurr);
# check for bad placement of section $InitAttribute (e.g.: __initdata)
if ($line =~ /(\b$InitAttribute\b)/) {
my $attr = $1;
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