On 2/25/20 08:17, Jani Nikula wrote:
> On Tue, 25 Feb 2020, "Gustavo A. R. Silva" <gustavo@xxxxxxxxxxxxxx> wrote:
>> The current codebase makes use of the zero-length array language
>> extension to the C90 standard, but the preferred mechanism to declare
>> variable-length types such as these ones is a flexible array member[1][2],
>> introduced in C99:
>>
>> struct foo {
>> int stuff;
>> struct boo array[];
>> };
>>
>> By making use of the mechanism above, we will get a compiler warning
>> in case the flexible array does not occur last in the structure, which
>> will help us prevent some kind of undefined behavior bugs from being
>> inadvertently introduced[3] to the codebase from now on.
>>
>> Also, notice that, dynamic memory allocations won't be affected by
>> this change:
>>
>> "Flexible array members have incomplete type, and so the sizeof operator
>> may not be applied. As a quirk of the original implementation of
>> zero-length arrays, sizeof evaluates to zero."[1]
>>
>> This issue was found with the help of Coccinelle.
>>
>> [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
>> [2] https://github.com/KSPP/linux/issues/21
>> [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
>>
>> Signed-off-by: Gustavo A. R. Silva <gustavo@xxxxxxxxxxxxxx>
>> ---
>> drivers/gpu/drm/etnaviv/etnaviv_gem.h | 2 +-
>> drivers/gpu/drm/gma500/intel_bios.h | 2 +-
>> drivers/gpu/drm/i915/display/intel_vbt_defs.h | 4 ++--
>> drivers/gpu/drm/i915/gt/intel_lrc.c | 2 +-
>> drivers/gpu/drm/i915/i915_gpu_error.h | 2 +-
>
> Please split out the i915 changes to a separate patch.
>
Sure thing. I can do that.
>> drivers/gpu/drm/msm/msm_gem.h | 2 +-
>> drivers/gpu/drm/qxl/qxl_cmd.c | 2 +-
>> drivers/gpu/drm/vboxvideo/vboxvideo.h | 2 +-
>> drivers/gpu/drm/vc4/vc4_drv.h | 2 +-
>> drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c | 2 +-
>> drivers/gpu/drm/vmwgfx/vmwgfx_surface.c | 2 +-
>> include/drm/bridge/mhl.h | 4 ++--
>> include/drm/drm_displayid.h | 2 +-
>> include/uapi/drm/i915_drm.h | 4 ++--
>
> Not sure it's worth touching uapi headers. They're full of both [0] and
> []. Again, please at least split it to a separate patch to be decided
> separately.
>
Yeah, it's worth it; the purpose of these patches is to replace [0] with [] across
the whole tree.
Thanks
--
Gustavo
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