Some compiler versions are smart enough to detect a potentially
uninitialized variable, but are not smart enough to detect that this
cannot happen due to the code flow:
../hw/intc/i8259.c: In function ‘pic_read_irq’:
../hw/intc/i8259.c:203:13: error: ‘irq2’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
203 | irq = irq2 + 8;
| ~~~~^~~~~~~~~~
Restrict irq2 variable use to the inner statement.
Fixes: 78ef2b6989f ("i8259: Reorder intack in pic_read_irq")
Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
---
Since v3:
- Declare irq2 really local (Richard)
Since v2:
- Remove pic_intack() call (Zoltan)
---
hw/intc/i8259.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
diff --git a/hw/intc/i8259.c b/hw/intc/i8259.c
index 344fd04db14..d67c4710f15 100644
--- a/hw/intc/i8259.c
+++ b/hw/intc/i8259.c
@@ -176,12 +176,13 @@ static void pic_intack(PICCommonState *s, int irq)
int pic_read_irq(DeviceState *d)
{
PICCommonState *s = PIC_COMMON(d);
- int irq, irq2, intno;
+ int irq, intno;
irq = pic_get_irq(s);
if (irq >= 0) {
if (irq == 2) {
- irq2 = pic_get_irq(slave_pic);
+ int irq2 = pic_get_irq(slave_pic);
+
if (irq2 >= 0) {
pic_intack(slave_pic, irq2);
} else {
@@ -189,20 +190,18 @@ int pic_read_irq(DeviceState *d)
irq2 = 7;
}
intno = slave_pic->irq_base + irq2;
+ pic_intack(s, irq);
+ irq = irq2 + 8;
} else {
intno = s->irq_base + irq;
+ pic_intack(s, irq);
}
- pic_intack(s, irq);
} else {
/* spurious IRQ on host controller */
irq = 7;
intno = s->irq_base + irq;
}
- if (irq == 2) {
- irq = irq2 + 8;
- }
-
#ifdef DEBUG_IRQ_LATENCY
printf("IRQ%d latency=%0.3fus\n",
irq,
--
2.26.2
On 3/19/21 3:23 PM, Philippe Mathieu-Daudé wrote: > Some compiler versions are smart enough to detect a potentially > uninitialized variable, but are not smart enough to detect that this > cannot happen due to the code flow: > > ../hw/intc/i8259.c: In function ‘pic_read_irq’: > ../hw/intc/i8259.c:203:13: error: ‘irq2’ may be used uninitialized in this function [-Werror=maybe-uninitialized] > 203 | irq = irq2 + 8; > | ~~~~^~~~~~~~~~ > > Restrict irq2 variable use to the inner statement. > > Fixes: 78ef2b6989f ("i8259: Reorder intack in pic_read_irq") > Reported-by: Christian Borntraeger <borntraeger@de.ibm.com> > Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com> > --- > Since v3: > - Declare irq2 really local (Richard) I forgot to keep: Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
On Fri, Mar 19, 2021 at 03:23:08PM +0100, Philippe Mathieu-Daudé wrote: > Some compiler versions are smart enough to detect a potentially > uninitialized variable, but are not smart enough to detect that this > cannot happen due to the code flow: > > ../hw/intc/i8259.c: In function ‘pic_read_irq’: > ../hw/intc/i8259.c:203:13: error: ‘irq2’ may be used uninitialized in this function [-Werror=maybe-uninitialized] > 203 | irq = irq2 + 8; > | ~~~~^~~~~~~~~~ > > Restrict irq2 variable use to the inner statement. > > Fixes: 78ef2b6989f ("i8259: Reorder intack in pic_read_irq") > Reported-by: Christian Borntraeger <borntraeger@de.ibm.com> > Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com> Looks ok. Acked-by: Michael S. Tsirkin <mst@redhat.com> Paolo, you merging this? > --- > Since v3: > - Declare irq2 really local (Richard) > Since v2: > - Remove pic_intack() call (Zoltan) > --- > hw/intc/i8259.c | 13 ++++++------- > 1 file changed, 6 insertions(+), 7 deletions(-) > > diff --git a/hw/intc/i8259.c b/hw/intc/i8259.c > index 344fd04db14..d67c4710f15 100644 > --- a/hw/intc/i8259.c > +++ b/hw/intc/i8259.c > @@ -176,12 +176,13 @@ static void pic_intack(PICCommonState *s, int irq) > int pic_read_irq(DeviceState *d) > { > PICCommonState *s = PIC_COMMON(d); > - int irq, irq2, intno; > + int irq, intno; > > irq = pic_get_irq(s); > if (irq >= 0) { > if (irq == 2) { > - irq2 = pic_get_irq(slave_pic); > + int irq2 = pic_get_irq(slave_pic); > + > if (irq2 >= 0) { > pic_intack(slave_pic, irq2); > } else { > @@ -189,20 +190,18 @@ int pic_read_irq(DeviceState *d) > irq2 = 7; > } > intno = slave_pic->irq_base + irq2; > + pic_intack(s, irq); > + irq = irq2 + 8; > } else { > intno = s->irq_base + irq; > + pic_intack(s, irq); > } > - pic_intack(s, irq); > } else { > /* spurious IRQ on host controller */ > irq = 7; > intno = s->irq_base + irq; > } > > - if (irq == 2) { > - irq = irq2 + 8; > - } > - > #ifdef DEBUG_IRQ_LATENCY > printf("IRQ%d latency=%0.3fus\n", > irq, > -- > 2.26.2
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