checkpatch: add --strict check for ifs with unnecessary parentheses

An if statement test like
	if ((foo == bar) && (baz != qux))
can arguably be better written without the parentheses as
	if (foo == bar && baz != qux)

Add a test to find these cases.

Link: http://lkml.kernel.org/r/dcd0561ddd0fa43c51a420d53b550d738bf42001.1502734458.git.joe@perches.com
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, 24 insertions, 0 deletions

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 2287a0bca863..143ab5ca2c41 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4496,6 +4496,30 @@ sub process {
                         }
                 }
 
+# check for unnecessary parentheses around comparisons in if uses
+                if ($^V && $^V ge 5.10.0 && defined($stat) &&
+                    $stat =~ /(^.\s*if\s*($balanced_parens))/) {
+                        my $if_stat = $1;
+                        my $test = substr($2, 1, -1);
+                        my $herectx;
+                        while ($test =~ /(?:^|[^\w\&\!\~])+\s*\(\s*([\&\!\~]?\s*$Lval\s*(?:$Compare\s*$FuncArg)?)\s*\)/g) {
+                                my $match = $1;
+                                # avoid parentheses around potential macro args
+                                next if ($match =~ /^\s*\w+\s*$/);
+                                if (!defined($herectx)) {
+                                        $herectx = $here . "\n";
+                                        my $cnt = statement_rawlines($if_stat);
+                                        for (my $n = 0; $n < $cnt; $n++) {
+                                                my $rl = raw_line($linenr, $n);
+                                                $herectx .=  $rl . "\n";
+                                                last if $rl =~ /^[ \+].*\{/;
+                                        }
+                                }
+                                CHK("UNNECESSARY_PARENTHESES",
+                                    "Unnecessary parentheses around '$match'\n" . $herectx);
+                        }
+                }
+
 #goto labels aren't indented, allow a single space however
                 if ($line=~/^.\s+[A-Za-z\d_]+:(?![0-9]+)/ and
                    !($line=~/^. [A-Za-z\d_]+:/) and !($line=~/^.\s+default:/)) {