Re: [Xen-devel] [PATCH] tools/kdd: silence gcc 8 warning a different way

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, Apr 12, 2018 at 06:04:49AM -0600, Jan Beulich wrote:
> Older gcc doesn't like "#pragma GCC diagnostic" inside functions.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> --- a/tools/debugger/kdd/kdd.c
> +++ b/tools/debugger/kdd/kdd.c
> @@ -695,10 +695,10 @@ static void kdd_handle_read_ctrl(kdd_sta
>              KDD_LOG(s, "Request outside of known control space\n");
>              len = 0;
>          } else {
> -#pragma GCC diagnostic push
> -#pragma GCC diagnostic ignored "-Warray-bounds"
> -            memcpy(buf, ((uint8_t *)&ctrl.c32) + offset, len);
> -#pragma GCC diagnostic pop
> +            /* Suppress bogus gcc 8 "out of bounds" warning. */
> +            const uint8_t *src;
> +            asm ("" : "=g" (src) : "0" ((uint8_t *)&ctrl.c32 + offset));
> +            memcpy(buf, src, len);

The code looks correct to me:

Reviewed-by: Wei Liu <wei.liu2@xxxxxxxxxx>

This will hopefully also fix the issue Boris reported that some older
gcc (<4.6) doesn't support push and pop.

This is the first time I see inline assembly is used to silence gcc.
;-)

>          }
>      }
>  
> 
> 
> 

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