Sparse errors

[Takashi Iwai]

On Wed, 26 May 2021 16:17:18 +0200,
Pierre-Louis Bossart wrote:
> 
> 
> 
> On 5/26/21 2:40 AM, Takashi Iwai wrote:
> > On Tue, 25 May 2021 21:32:27 +0200,
> > Pierre-Louis Bossart wrote:
> >>
> >> Hi Takashi,
> >> Sparse reports a lot of new issues in our last checks with more options:
> >>
> >> export ARCH=x86_64 CF="-Wsparse-error -Wsparse-all
> >> -Wno-bitwise-pointer -Wno-pointer-arith -Wno-typesign -Wnoshadow
> >> -Wno-sizeof-bool"
> >> make -k sound/ C=2
> >>
> >> most are linked to the __user and pcm_format_t restricted types, but I
> >> found the simpler ones below which are useless comparisons. I can send
> >> a patch for the last but not sure how to address the first two.
> >>
> >> Thanks for your feedback
> >> -Pierre
> >>
> >> sound/core/info.c:95:38: error: self-comparison always evaluates to false
> >>
> >> 	if (pos < 0 || (long) pos != pos || (ssize_t) count < 0)
> >> 		return false;
> >>
> >> not sure what the second comparison is meant to check?
> >
> > As Dan suggested, it's a check only for 32bit architecture for a 64bit
> > value.
> 
> Isn't there a better way to check this?

Sure, there are hundreds other ways, but they might be longer :)
If any, a comment would be deserved.

> >> sound/drivers/opl3/opl3_midi.c:183:60: error: self-comparison always
> >> evaluates to false
> >>
> >> This indeed makes no sense. the voice_time and vp->time are not
> >> changed in the loop, the test is either redundant or something else is
> >> missing.
> >
> > The code doesn't look right, indeed.  It's likely meant to be vp2
> > instead of vp.
> >
> > --- a/sound/drivers/opl3/opl3_midi.c
> > +++ b/sound/drivers/opl3/opl3_midi.c
> > @@ -180,8 +180,7 @@ static int opl3_get_voice(struct snd_opl3 *opl3, int instr_4op,
> >   			if (vp2->state == SNDRV_OPL3_ST_ON_2OP) {
> >   				/* kill two voices, EXPENSIVE */
> >   				bp++;
> > -				voice_time = (voice_time > vp->time) ?
> > -					voice_time : vp->time;
> > +				voice_time = max(voice_time, vp2->time);
> >   			}
> >   		} else {
> >   			/* allocate 2op voice */
> 
> It's really old code, unchanged since the first git commit in
> 2005... Are you comfortable changing this code? One of those cases
> where if people didn't notice an issue in 16+ years maybe no one cares
> or even uses this driver...

It'll be a safe change, so I'd apply the fix.

It's about the choice of an OPL3 voice, and the function tries to find
the best one.  The code seems to want to align with the timestamp of
the coupled voice, and even if it's not right, the impact is very
limited.


thanks,

Takashi