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@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 27 insertions, 0 deletions

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index c43be815cc71..c2d223c406e8 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",