[PATCH 1/2] Don't clobber virtual core pointer touches array length

[Peter Hutterer]

On Mon, Feb 13, 2012 at 04:00:47PM -0800, Chase Douglas wrote:
> When copying the touch class, the VCP has its own touches array. The
> length of this array must be kept alongside the array itself or we get
> memory corruption.
> 
> Signed-off-by: Chase Douglas <chase.douglas at canonical.com>
> ---
>  Xi/exevents.c |    9 ++++++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/Xi/exevents.c b/Xi/exevents.c
> index 671c051..51f991c 100644
> --- a/Xi/exevents.c
> +++ b/Xi/exevents.c
> @@ -671,7 +671,8 @@ DeepCopyPointerClasses(DeviceIntPtr from, DeviceIntPtr to)
>  
>      if (from->touch)
>      {
> -        TouchPointInfoPtr tmp;
> +        TouchPointInfoPtr to_touches_array_tmp;
> +        int to_num_touches_tmp;
>          if (!to->touch)
>          {
>              classes = to->unused_classes;
> @@ -692,9 +693,11 @@ DeepCopyPointerClasses(DeviceIntPtr from, DeviceIntPtr to)
>              } else
>                  classes->touch = NULL;
>          }
> -        tmp = to->touch->touches;
> +        to_touches_array_tmp = to->touch->touches;
> +        to_num_touches_tmp = to->touch->num_touches;
>          memcpy(to->touch, from->touch, sizeof(TouchClassRec));
> -        to->touch->touches = tmp;
> +        to->touch->touches = to_touches_array_tmp;
> +        to->touch->num_touches = to_num_touches_tmp;
>          to->touch->sourceid = from->id;
>      } else if (to->touch)
>      {
> -- 
> 1.7.9

quite frankly, I think copying the fields separately instead of a memcpy and
then overwrite-back is the better idea here. with a rather simple test-case,
we can also ensure that this doesn't break when the class changes.

Cheers,
  Peter