[alsa-devel] Question about the right fix for a sparse warning

[Takashi Iwai]

On Wed, 29 Jan 2020 18:01:00 +0100,
Pierre-Louis Bossart wrote:
> 
> 
> 
> >>>> We're seeing the following sparse warning in the SOF code:
> >>>>
> >>>> sound/soc/sof/sof-audio.c:86:31: warning: incorrect type in assignment (different base types)
> >>>> sound/soc/sof/sof-audio.c:86:31:    expected restricted snd_pcm_state_t [usertype] state
> >>>> sound/soc/sof/sof-audio.c:86:31:    got signed int [signed] [usertype] [explicitly-signed] state
> >>>>
> >>>> The line under scrutiny where we assign "state" is as follows:
> >>>>
> >>>> state = substream->runtime->status->state;
> >>>>
> >>>> and it is defined as
> >>>> snd_pcm_state_t state;
> >>>>
> >>>> There are other places (ex pcm_oss.c) where a similar assignment has been used
> >>>> as well.
> >>>>
> >>>> What fixes the issue is a forced cast to snd_pcm_state_t as below before
> >>>> assigning:
> >>>>    state = (__force snd_pcm_state_t)substream->runtime->status->state;
> >>>>
> >>>> Do you think this is acceptable? If not, could you please suggest an
> >>>> alternative?
> >>>
> >>> Hm, I don't see the warning in my code.  Did you merge all upstream
> >>> stuff and still get it?
> >>
> >> It's been merged in the SOF tree (topic/sof-dev) and it'll be in the
> >> next batch I send. It's not upstream just yet because we want to
> >> remove the warning to make the patch nice and shiny :-)
> >
> > I still wonder why I couldn't get it on my tree.  I guess the code
> > around that hasn't changed, right?
> >
> > Wait...  Is it a test on 32bit arch?  If so, it might be a new thing
> > for y2038 support.  Then we may fix the uapi definition instead.
> 
> It's actually in your tree already, my mistake, see:
> 
> ee1e79b72e3cf ("ASoC: SOF: partition audio-related parts from SOF core")
> 
> It's with plain-vanilla x86_64, I can share the config.

Sorry, my bad, it seems that my sparse program was too old.  After
upgrading to the latest version, I could see the warning, too.


Takashi