On Tue, 29 Jan 2013, Joe Perches wrote: > On Tue, 2013-01-29 at 10:55 -0500, Valdis.Kletnieks@xxxxxx wrote: > > On Sun, 27 Jan 2013 23:19:47 +0300, Dan Carpenter said: > > > > > Yeah. I think it would be, but adding bitflags together instead of > > > doing bitwise ORs is very common as well. > > > > The fact it's common doesn't mean it's good programming practice, > > or even correct. Consider: > > > > #define F_FOO 0x01 > > #define F_BAR 0x02 > > #define F_BAZ 0x04 > > > > unsigned int flags = F_FOO; > > ... > > flags |= F_BAR; > > > > Now some time later, another code path does this: > > > > flags += F_FOO; > > > > If it was another |, it would be a no harm no foul class of bug. > > But how long is it going to take you to figure out who set F_BAZ? > > > > I wonder if there's a way to write a coccinelle patch to find places > > where we do arithmetic operations on bitmasks.... > > Not so far as I know, but maybe someone on the > cocci lists does. (cc'd) > > I could imagine a test for variables that have > uses of both arithmetic and bit operations but > not a discriminator for when one type is > appropriate and the other is not. If the definition of a bitmask is an identifier in all capital letters, that would be easy. Another possibility is such an identifier that is defined to a value expressed beginning with 0x. Another possibility is such an identifier that is sometimes used with & and | and sometimes used with an arithmetic operation. I will give them a try. julia -- To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
