From: Joe Perches <joe@perches.com>
To: Andy Whitcroft <apw@shadowen.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
Jacob Pan <jacob.jun.pan@linux.intel.com>
Subject: Re: [PATCH] checkpatch: Warn on comparisons to true and false
Date: Wed, 10 Apr 2013 04:27:51 -0700 [thread overview]
Message-ID: <1365593271.27174.35.camel@joe-AO722> (raw)
In-Reply-To: <20130410093346.GO7511@dm>
On Wed, 2013-04-10 at 10:33 +0100, Andy Whitcroft wrote:
> On Tue, Apr 09, 2013 at 08:17:14PM -0700, Joe Perches wrote:
> > Comparisons of A to true and false are better written
> > as A and !A.
[]
> In a complex case such as a + b == false will this do the right thing?
Very sensible question. No it won't.
checkpatch doesn't understand expressions
very well nor does it understand precedence
operations between expressions and tests.
I did run it against the kernel tree and there
weren't any I noticed like that though.
> Not that I am sure that adding bools makes sense but assuming there is
> some valid complex lval.
$Lval in this case is a single variable and
is neither a function nor an expression.
It doesn't match on:
if (func(x, y) == true)
or
if ((x | y) == true)
because of the ) before the ==
It will falsely match on expressions like:
if (x + y == true)
but as far as I can tell there aren't any
uses like that in the kernel tree.
$ git grep -E "(==|\!=)\s*(true|false)\b" | \
cut -f2- -d":" |grep -P "\b(\+|\-)\b"
nor are there any and/or bit operator.
When I tried adding a test for:
"$Constant == $Lval"
instead of
"$Lval == $Constant"
like
0 == foo
instead of
foo == 0
there were _way_ too many false positives of
the $Expression sort that I didn't add that test.
cheers, Joe
next prev parent reply other threads:[~2013-04-10 11:27 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-10 3:17 [PATCH] checkpatch: Warn on comparisons to true and false Joe Perches
2013-04-10 9:33 ` Andy Whitcroft
2013-04-10 11:27 ` Joe Perches [this message]
2013-04-10 12:41 ` Andy Whitcroft
2013-04-10 22:57 ` Andrew Morton
2013-04-11 1:07 ` Joe Perches
2013-04-11 2:14 ` Dave Jones
2013-04-11 3:47 ` Joe Perches
2013-04-11 8:19 ` Dan Carpenter
2013-04-11 8:29 ` Joe Perches
2013-04-11 11:56 ` Bjørn Mork
2013-04-11 14:25 ` Joe Perches
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