Re: [Qemu-devel] [PATCH 3/4] s390-ccw.img: Fix compile warning in s390 ccw virtio code

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 23/04/13 13:31, Alexander Graf wrote:
> On 04/23/2013 01:23 PM, Christian Borntraeger wrote:
>> Lets fix this gcc warning:
>>
>> virtio.c: In function ‘vring_send_buf’:
>> virtio.c:125:35: error: operation on ‘vr->next_idx’ may be undefined
>> [-Werror=sequence-point]
>>
>> Signed-off-by: Christian Borntraeger<borntraeger@de.ibm.com>
>> ---
>>   pc-bios/s390-ccw/virtio.c | 4 +++-
>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/pc-bios/s390-ccw/virtio.c b/pc-bios/s390-ccw/virtio.c
>> index 79e2941..1968fc6 100644
>> --- a/pc-bios/s390-ccw/virtio.c
>> +++ b/pc-bios/s390-ccw/virtio.c
>> @@ -122,7 +122,9 @@ static void vring_send_buf(struct vring *vr, void *p, int len, int flags)
>>       vr->desc[vr->next_idx].addr = (ulong)p;
>>       vr->desc[vr->next_idx].len = len;
>>       vr->desc[vr->next_idx].flags = flags&  ~VRING_HIDDEN_IS_CHAIN;
>> -    vr->desc[vr->next_idx].next = ++vr->next_idx;
>> +    vr->desc[vr->next_idx].next = vr->next_idx;
>> +    vr->desc[vr->next_idx].next++;
>> +    vr->next_idx++;
> 
> Hrm. This looks a lot more complicated than it needs to. Why is gcc emitting a warning here? Maybe it only wants braces. Please try whether
> 
> .next = ++(vr->next_id);
> 
> works for you.
> 
> 
> Alex
> 
> 

I already did that, but I get the same error message. I dont understand why gcc emits that warning,
but it does :-(