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

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 3/18/21 5:11 PM, Christian Borntraeger wrote:
> On 18.03.21 17:03, Paolo Bonzini wrote:
>> 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:
> 
> This also works, but if you want to go down that path then it would be
> good if you
> could do this patch as I do not have the testing infrastructure to do
> proper x86
> changes.
>>
>> 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;
>> -    }
>> -

This looks like the patch I just sent :)