Re: [PATCH] intc/i8259: avoid (false positive) gcc warning

[Paolo Bonzini]

On 18/03/21 16:47, Christian Borntraeger wrote:
> some copiler 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;
>         |         ~~~~^~~~~~~~~~
>
> Let us initialize irq2 to -1 to avoid this warning as the most simple
> solution.

What about:

diff --git a/hw/intc/i8259.c b/hw/intc/i8259.c
index 344fd04db1..bf28c179de 100644
--- a/hw/intc/i8259.c
+++ b/hw/intc/i8259.c
@@ -189,20 +189,18 @@ int pic_read_irq(DeviceState *d)
                 irq2 = 7;
             }
             intno = slave_pic->irq_base + irq2;
+            irq = irq2 + 8;
+            pic_intack(s, 2);
         } 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,


?

Paolo