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checkpatch: add constant comparison on left side test

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"CONST <comparison> variable" checks like:

        if (NULL != foo)
and
        while (0 < bar(...))

where a constant (or what appears to be a constant like an upper case
identifier) is on the left of a comparison are generally preferred to be
written using the constant on the right side like:

        if (foo != NULL)
and
        while (bar(...) > 0)

Add a test for this.

Add a --fix option too, but only do it when the code is immediately
surrounded by parentheses to avoid misfixing things like "(0 < bar() +
constant)"

Signed-off-by: Joe Perches <joe@perches.com>
Cc: Nicolas Morey Chaisemartin <nmorey@kalray.eu>
Cc: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Joe Perches 2015-09-09 15:37:58 -07:00 committed by Linus Torvalds
parent 54507b5183
commit c5595fa2f1
1 changed files with 29 additions and 0 deletions
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29
scripts/checkpatch.pl
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@ -4231,6 +4231,35 @@ sub process {
}
}
# comparisons with a constant or upper case identifier on the left
# avoid cases like "foo + BAR < baz"
# only fix matches surrounded by parentheses to avoid incorrect
# conversions like "FOO < baz() + 5" being "misfixed" to "baz() > FOO + 5"
if ($^V && $^V ge 5.10.0 &&
$line =~ /^\+(.*)\b($Constant|[A-Z_][A-Z0-9_]*)\s*($Compare)\s*($LvalOrFunc)/) {
my $lead = $1;
my $const = $2;
my $comp = $3;
my $to = $4;
my $newcomp = $comp;
if ($lead !~ /$Operators\s*$/ &&
$to !~ /^(?:Constant|[A-Z_][A-Z0-9_]*)$/ &&
WARN("CONSTANT_COMPARISON",
"Comparisons should place the constant on the right side of the test\n" . $herecurr) &&
$fix) {
if ($comp eq "<") {
$newcomp = ">";
} elsif ($comp eq "<=") {
$newcomp = ">=";
} elsif ($comp eq ">") {
$newcomp = "<";
} elsif ($comp eq ">=") {
$newcomp = "<=";
}
$fixed[$fixlinenr] =~ s/\(\s*\Q$const\E\s*$Compare\s*\Q$to\E\s*\)/($to $newcomp $const)/;
}
}
# Return of what appears to be an errno should normally be negative
if ($sline =~ /\breturn(?:\s*\(+\s*|\s+)(E[A-Z]+)(?:\s*\)+\s*|\s*)[;:,]/) {
my $name = $1;