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

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Message-ID: <20250407182750.GA1727154@ziepe.ca>
Date: Mon, 7 Apr 2025 15:27:50 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Arnd Bergmann <arnd@...nel.org>
Cc: Dennis Dalessandro <dennis.dalessandro@...nelisnetworks.com>,
	Leon Romanovsky <leon@...nel.org>, Arnd Bergmann <arnd@...db.de>,
	"Steven Rostedt (Google)" <rostedt@...dmis.org>,
	Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
	Jani Nikula <jani.nikula@...el.com>,
	Christian König <christian.koenig@....com>,
	"Dr. David Alan Gilbert" <linux@...blig.org>,
	Maher Sanalla <msanalla@...dia.com>, linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] RDMA/hfi1: use a struct group to avoid warning

On Thu, Apr 03, 2025 at 04:47:53PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> 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