linux-kernel - [PATCH 09/12] checkpatch: Add a --strict test for comparison to true/false

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Date:	Mon, 10 Jun 2013 15:20:47 -0700
From:	Joe Perches <joe@...ches.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andy Whitcroft <apw@...onical.com>, linux-kernel@...r.kernel.org
Subject: [PATCH 09/12] checkpatch: Add a --strict test for comparison to true/false

Comparing to true or false is error prone.

Add tests for the various forms of (foo == true) && (false != bar)
that are only reported with --strict.

Signed-off-by: Joe Perches <joe@...ches.com>
---
 scripts/checkpatch.pl | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index c43be81..c2d223c 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -3588,6 +3588,33 @@ sub process {
 			     "Using yield() is generally wrong. See yield() kernel-doc (sched/core.c)\n"  . $herecurr);
 		}
 
+# check for comparisons against true and false
+		if ($line =~ /\+\s*(.*?)\b(true|false|$Lval)\s*(==|\!=)\s*(true|false|$Lval)\b(.*)$/i) {
+			my $lead = $1;
+			my $arg = $2;
+			my $test = $3;
+			my $otype = $4;
+			my $trail = $5;
+			my $op = "!";
+
+			($arg, $otype) = ($otype, $arg) if ($arg =~ /^(?:true|false)$/i);
+
+			my $type = lc($otype);
+			if ($type =~ /^(?:true|false)$/) {
+				if (("$test" eq "==" && "$type" eq "true") ||
+				    ("$test" eq "!=" && "$type" eq "false")) {
+					$op = "";
+				}
+
+				CHK("BOOL_COMPARISON",
+				    "Using comparison to $otype is error prone\n" . $herecurr);
+
+## maybe suggesting a correct construct would better
+##				    "Using comparison to $otype is error prone.  Perhaps use '${lead}${op}${arg}${trail}'\n" . $herecurr);
+
+			}
+		}
+
 # check for semaphores initialized locked
 		if ($line =~ /^.\s*sema_init.+,\W?0\W?\)/) {
 			WARN("CONSIDER_COMPLETION",
-- 
1.8.1.2.459.gbcd45b4.dirty

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