[PATCH for 6.0 v4] hw/intc/i8259: Refactor pic_read_irq() to avoid uninitialized variable

[Philippe Mathieu-Daudé]

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