[Mesa-dev] [PATCH 1/4] i965: Remove spurious casts in copy_image_with_memcpy()

[Matt Turner]

On Wed, Nov 19, 2014 at 3:35 AM, Kristian Høgsberg <krh at bitplanet.net> wrote:
> On Tue, Nov 18, 2014 at 9:02 PM, Chad Versace
> <chad.versace at linux.intel.com> wrote:
>> If a pointer points to raw, untyped memory and is never dereferenced,
>> then declare it as 'void*' instead of casting it to 'void*'.
>>
>> Signed-off-by: Chad Versace <chad.versace at linux.intel.com>
>> ---
>>  src/mesa/drivers/dri/i965/intel_copy_image.c | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/src/mesa/drivers/dri/i965/intel_copy_image.c b/src/mesa/drivers/dri/i965/intel_copy_image.c
>> index 341220c..cb44474 100644
>> --- a/src/mesa/drivers/dri/i965/intel_copy_image.c
>> +++ b/src/mesa/drivers/dri/i965/intel_copy_image.c
>> @@ -144,7 +144,7 @@ copy_image_with_memcpy(struct brw_context *brw,
>>                         int src_width, int src_height)
>>  {
>>     bool same_slice;
>> -   uint8_t *mapped, *src_mapped, *dst_mapped;
>> +   void *mapped, *src_mapped, *dst_mapped;
>
> Making these void * means that this code below:
>
>       src_mapped = mapped + ((src_y - map_y1) / src_bh) * src_stride +
>                             ((src_x - map_x1) / src_bw) * cpp;
>
> (same for dst_mapped) becomes arithmetic on void pointers. gcc
> supports that and treats it as uint8_t pointer arithmetic [1], but I'm
> not aware of any official C standard that allows it.  I don't think we
> rely on that elsewhere

We have in the past, and using gcc extensions are fine. But as you
say, it's probably  not what he wanted anyway.