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
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