2021-12-11 18:19:38

by Colin Ian King

Subject: ALSA: drivers: opl3: assignment of a pointer that is not used, probable bug

Hi,

static analysis with scan-build has found an assignment to vp2 that is
never used in function snd_opl3_note_on(),
sound/drivers/opl3/opl3_midi.c as follows:

if (instr_4op) {
vp2 = &opl3->voices[voice + 3];
if (vp->state > 0) {
opl3_reg = reg_side | (OPL3_REG_KEYON_BLOCK +
voice_offset + 3);
reg_val = vp->keyon_reg & ~OPL3_KEYON_BIT;
opl3->command(opl3, opl3_reg, reg_val);
}
}

sound/drivers/opl3/opl3_midi.c:399:3: warning: Value stored to 'vp2' is
never read [deadcode.DeadStores]
vp2 = &opl3->voices[voice + 3];
^ ~~~~~~~~~~~~~~~~~~~~~~~~

I suspect that references to vp in this if block should be to vp2, but
I'm unsure if that is for all references or not, hence I'm reporting
this issue.

Coln

2021-12-12 09:00:37

by Takashi Iwai

Subject: Re: ALSA: drivers: opl3: assignment of a pointer that is not used, probable bug

On Sat, 11 Dec 2021 19:19:30 +0100,
Colin King (gmail) wrote:
>
> Hi,
>
> static analysis with scan-build has found an assignment to vp2 that is
> never used in function snd_opl3_note_on(),
> sound/drivers/opl3/opl3_midi.c as follows:
>
> if (instr_4op) {
> vp2 = &opl3->voices[voice + 3];
> if (vp->state > 0) {
> opl3_reg = reg_side | (OPL3_REG_KEYON_BLOCK +
> voice_offset + 3);
> reg_val = vp->keyon_reg & ~OPL3_KEYON_BIT;
> opl3->command(opl3, opl3_reg, reg_val);
> }
> }
>
> sound/drivers/opl3/opl3_midi.c:399:3: warning: Value stored to 'vp2'
> is never read [deadcode.DeadStores]
> vp2 = &opl3->voices[voice + 3];
> ^ ~~~~~~~~~~~~~~~~~~~~~~~~
>
> I suspect that references to vp in this if block should be to vp2, but
> I'm unsure if that is for all references or not, hence I'm reporting
> this issue.

Yes, the next vp->state > 0 check must be vp2->state > 0.
Care to submit a proper fix patch?


Thanks!

Takashi