On Sat, Oct 08, 2016 at 10:58:41AM -0400, Valdis.Kletnieks@xxxxxx wrote:
> On Sat, 08 Oct 2016 10:40:37 -0000, Nicholas Mc Guire said:
>
> > } else if (rtlpcipriv->bt_coexist.bt_service == BT_PAN) {
> > rtl_write_byte(rtlpriv, REG_GPIO_MUXCFG, tmp1byte);
> > } else {
> > rtl_write_byte(rtlpriv, REG_GPIO_MUXCFG, tmp1byte);
> > }
>
> That *does* smell like a bug. If nothing else, the last 'else if'
> can be removed. Most likely case: somebody cut-n-pasted that last
> section in and failed to change it to a proper 'default' value
> and the code falls through to that one rarely enough that nobody has
> noticed.
>
> > I personally find this irritating as (without a comment) it is hard to say
> > if this is a trivial type -> missed case, or if this is
> > intended as a default behavior.
>
> Unfortunately, it will probably be a really rough job figuring out what
> exactly was intended in each case. Figuring it out in filesystem code
> or other similar areas of the kernel wouldn't be too bad - but if it's
> a hardware driver, you're going to have to ask an expert (or somebody who
> has the hardware) for help.
Actually fs had one legitimate case where the positional side-effect was in use
<snip: fs/kernfs/file.c:kernfs_fop_open()>
* Both paths of the branch look the same. They're supposed to
* look that way and give @of->mutex different static lockdep keys.
*/
if (has_mmap)
mutex_init(&of->mutex);
else
mutex_init(&of->mutex);
<snip>
but almost all of the other cases look phony
>
> How did you find there were 90 of them? Did you cook up a Coccinelle script
> for it?
>
simple cocci script - Im checking through the reported cases to
see if it is actually reliable. In some cases it was obvious bugs (cut&paste
type) but in others it does seem to be a "coding pattern".
> If nothing else, cooking up a test to toss into scripts/coccinelle/misc
> would probably be a Good Thing...
Thats actually the cause of this mail - it just becaem obvious
that some of these if==else are intentional
Now reporting these cases if they should be fixed makes sense
while if this is accepted practice then it would be reporting
false-positives, which would be bad.
thx!
hofrat
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