Re: sparse: ARRAY_SIZE and sparse array initialization

[Hans Verkuil <hverkuil@xs4all.nl>]

Is there any chance that the three issues I reported will be fixed? If not,
then I'll work around it in the kernel code.

Regards,

	Hans

On 03/15/2014 01:12 PM, Hans Verkuil wrote:
> For the record: all these tests were done with a 3.14-rc5 kernel and sparse
> compiled from the git tree as of today (version v0.5.0). The gcc version is 4.8.2.
> 
> Regards,
> 
> 	Hans
> 
> On 03/15/2014 01:09 PM, Hans Verkuil wrote:
>> Hmm, interesting. Twice 'sparse' in the same subject line with different meanings :-)
>>
>> This is another sparse error I get with drivers/media/v4l2-core/v4l2-ioctl.c:
>>
>> drivers/media/v4l2-core/v4l2-ioctl.c:424:9: error: cannot size expression
>>
>> (there are more of those in drivers/media, all with the same cause).
>>
>> This sparse (the tool) error occurs because of sparse (C language) array initialization
>> in combination with ARRAY_SIZE:
>>
>> static const char *v4l2_memory_names[] = {
>>         [V4L2_MEMORY_MMAP]    = "mmap",
>>         [V4L2_MEMORY_USERPTR] = "userptr",
>>         [V4L2_MEMORY_OVERLAY] = "overlay",
>>         [V4L2_MEMORY_DMABUF] = "dmabuf",
>> };
>>
>> #define prt_names(a, arr) (((unsigned)(a)) < ARRAY_SIZE(arr) ? arr[a] : "unknown")
>>
>> static void v4l_print_requestbuffers(const void *arg, bool write_only)
>> {
>>         const struct v4l2_requestbuffers *p = arg;
>>
>>         pr_cont("count=%d, type=%s, memory=%s\n",
>>                 p->count,
>>                 prt_names(p->type, v4l2_type_names),
>>                 prt_names(p->memory, v4l2_memory_names));
>> }
>>
>> I could change v4l2_memory_names to:
>>
>> static const char *v4l2_memory_names[V4L2_MEMORY_DMABUF + 1] = {
>>
>> and the error goes away.
>>
>> I'm actually not sure if this is a sparse bug or a feature.
>>
>> If it is a feature then the error message is definitely wrong, since the size is
>> perfectly well defined. As an aside: the error message is pretty vague IMHO.
>>
>> Regards,
>>
>> 	Hans
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