Messages in this thread | | | Subject | coccinelle and bitmask arithmetic (was: Re: [patch] TTY: synclink, small cleanup in dtr_rts()) | From | Joe Perches <> | Date | Tue, 29 Jan 2013 08:13:18 -0800 |
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On Tue, 2013-01-29 at 10:55 -0500, Valdis.Kletnieks@vt.edu 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.
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