Re: [Xen-devel] [PATCH 1/2] x86/e820: fix build with gcc9

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Thu, Mar 07, 2019 at 03:31:43AM -0700, Jan Beulich wrote:
> e820.c: In function ‘clip_to_limit’:
> .../xen/include/asm/string.h:10:26: error: ‘__builtin_memmove’ offset [-16, 
> -36] is out of the bounds [0, 20484] of
> object ‘e820’ with type ‘struct e820map’ [-Werror=array-bounds]
>    10 | #define memmove(d, s, n) __builtin_memmove(d, s, n)
>       |                          ^~~~~~~~~~~~~~~~~~~~~~~~~~
> e820.c:404:13: note: in expansion of macro ‘memmove’
>   404 |             memmove(&e820.map[i], &e820.map[i+1],
>       |             ^~~~~~~
> e820.c:36:16: note: ‘e820’ declared here
>    36 | struct e820map e820;
>       |                ^~~~
> 
> While I can't see where the negative offsets would come from, converting
> the loop index to unsigned type helps. Take the opportunity and also
> convert several other local variables and copy_e820_map()'s second
> parameter to unsigned int (and bool in one case).

I also cannot see how you can end up with negative offsets, but
changing to unsigned int is definitely and improvement IMO.

> Reported-by: Charles Arnold <carnold@xxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Thanks.

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