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Date:   Fri, 11 Feb 2022 14:05:23 -0800
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Cc:     linux-kernel@vger.kernel.org,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Subject: Re: [PATCH] container_of.h: make container_of const-aware
Message-Id: <20220211140523.738c14327b03647f535c4df8@linux-foundation.org>
In-Reply-To: <20220210170434.3924169-1-dmitry.baryshkov@linaro.org>
References: <20220210170434.3924169-1-dmitry.baryshkov@linaro.org>
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On Thu, 10 Feb 2022 20:04:34 +0300 Dmitry Baryshkov <dmitry.baryshkov@linaro.org> wrote:

> container_of() macro has one major drawback. It does not check whether
> the passed ptr has a const pointer, the result will always be a
> non-const pointer. Use a _Generic() construct (supported since gcc 4.9
> and Clang 3.0) to teach container_of that if converting a const pointer,
> the returned pointer should also have the const modifier.
> 

Nice idea, but my x86_64 allnoconfig build explodes with zillions of
warnings.

In file included from ./include/linux/list.h:5,
                 from ./include/linux/module.h:12,
                 from init/do_mounts.c:2:
./include/net/sock.h: In function 'sk_entry':
./include/linux/container_of.h:17:42: warning: return discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]