Re: [PATCH] RDMA/hfi1: use a struct group to avoid warning

[Jason Gunthorpe]

On Thu, Apr 03, 2025 at 04:47:53PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
> 
> On gcc-11 and earlier, the driver sometimes produces a warning
> for memset:
> 
> In file included from include/linux/string.h:392,
>                  from drivers/infiniband/hw/hfi1/mad.c:6:
> In function 'fortify_memset_chk',
>     inlined from '__subn_get_opa_hfi1_cong_log' at drivers/infiniband/hw/hfi1/mad.c:3873:2,
>     inlined from 'subn_get_opa_sma' at drivers/infiniband/hw/hfi1/mad.c:4114:9:
> include/linux/fortify-string.h:480:4: error: call to '__write_overflow_field' declared with attribute warning: detected write beyond size of field (1st parameter); maybe use struct_group()? [-Werror]
>     __write_overflow_field(p_size_field, size);
>     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> This seems to be a false positive, and I found no nice way to rewrite
> the code to avoid the warning, but adding a a struct group works.

Er.. so do we really want to fix it or just ignore this on gcc-11? Or
is there really a compile bug here and it is mis-generating the code?

The unneeded struct group seems ugly to me?

Jason