Re: [PATCH] hw/display/xenfb: Replace unreachable code by abort()

[Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>]

On 29/7/25 13:12, Markus Armbruster wrote:
> xenfb_mouse_event() has a switch statement whose controlling
> expression move->axis is an enum InputAxis.  The enum values are
> INPUT_AXIS_X and INPUT_AXIS_Y, encoded as 0 and 1.  The switch has a
> case for both axes.  In addition, it has an unreachable default label.
> This convinces Coverity that move->axis can be greater than 1.  It
> duly reports a buffer overrun when it is used to subscript an array
> with two elements.
>
> Replace the unreachable code by abort().
>
> Resolves: Coverity CID 1613906
> Signed-off-by: Markus Armbruster <armbru@xxxxxxxxxx>
> ---
>   hw/display/xenfb.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/hw/display/xenfb.c b/hw/display/xenfb.c
> index 22822fecea..5e6c691779 100644
> --- a/hw/display/xenfb.c
> +++ b/hw/display/xenfb.c
> @@ -283,8 +283,7 @@ static void xenfb_mouse_event(DeviceState *dev, QemuConsole 
> *src,
>                   scale = surface_height(surface) - 1;
>                   break;
>               default:
> -                scale = 0x8000;
> -                break;
> +                abort();
We prefer GLib g_assert_not_reached() over abort() because it displays
the file, line number & function before aborting.

>               }
>               xenfb->axis[move->axis] = move->value * scale / 0x7fff;
>           }