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Re: [Qemu-devel] [PATCH 14/14] hw/s390x/3270-ccw: avoid taking address o


From: David Hildenbrand
Subject: Re: [Qemu-devel] [PATCH 14/14] hw/s390x/3270-ccw: avoid taking address of fields in packed struct
Date: Fri, 29 Mar 2019 12:42:14 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0

On 29.03.19 12:11, Daniel P. Berrangé wrote:
> Compiling with GCC 9 complains
> 
> hw/s390x/3270-ccw.c: In function ‘emulated_ccw_3270_cb’:
> hw/s390x/3270-ccw.c:81:19: error: taking address of packed member of ‘struct 
> SCHIB’ may result in an unaligned pointer value 
> [-Werror=address-of-packed-member]
>    81 |         SCSW *s = &sch->curr_status.scsw;
>       |                   ^~~~~~~~~~~~~~~~~~~~~~
> 
> This local variable is only present to save a little bit of
> typing when setting the field later. Get rid of this to avoid
> the warning about unaligned accesses.
> 
> Signed-off-by: Daniel P. Berrangé <address@hidden>
> ---
>  hw/s390x/3270-ccw.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/hw/s390x/3270-ccw.c b/hw/s390x/3270-ccw.c
> index 2c8d16ccf7..14882242c3 100644
> --- a/hw/s390x/3270-ccw.c
> +++ b/hw/s390x/3270-ccw.c
> @@ -78,13 +78,13 @@ static int emulated_ccw_3270_cb(SubchDev *sch, CCW1 ccw)
>  
>      if (rc == -EIO) {
>          /* I/O error, specific devices generate specific conditions */
> -        SCSW *s = &sch->curr_status.scsw;
> +        SCHIB *schib = &sch->curr_status;
>  
>          sch->curr_status.scsw.dstat = SCSW_DSTAT_UNIT_CHECK;
>          sch->sense_data[0] = 0x40;    /* intervention-req */
> -        s->ctrl &= ~SCSW_ACTL_START_PEND;
> -        s->ctrl &= ~SCSW_CTRL_MASK_STCTL;
> -        s->ctrl |= SCSW_STCTL_PRIMARY | SCSW_STCTL_SECONDARY |
> +        schib->scsw.ctrl &= ~SCSW_ACTL_START_PEND;
> +        schib->scsw.ctrl &= ~SCSW_CTRL_MASK_STCTL;
> +        schib->scsw.ctrl |= SCSW_STCTL_PRIMARY | SCSW_STCTL_SECONDARY |
>                     SCSW_STCTL_ALERT | SCSW_STCTL_STATUS_PEND;

Don't like that way of indenting.

Reviewed-by: David Hildenbrand <address@hidden>

>      }
>  
> 


-- 

Thanks,

David / dhildenb



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