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From:   Rong Tao <rtoax@foxmail.com>
To:     sj@kernel.org
Cc:     damon@lists.linux.dev, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, linux-mm@kvack.org,
        rongtao@cestc.cn, rtoax@foxmail.com, shuah@kernel.org,
        yuanchu@google.com
Subject: Re: Re: [PATCH] selftests/damon: Fix unnecessary compilation warnings
Date:   Sat, 12 Nov 2022 13:01:04 +0800
In-Reply-To: <20221111173855.108360-1-sj@kernel.org>
References: <20221111173855.108360-1-sj@kernel.org>
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Hi, Park, I just search on GCC source code, found GCC support
"-Wstringop-overread" at least gcc-11.1.0, commit d14c547abd48("Add
-Wstringop-overread for reading past the end by string functions.").

AND found a testsuite gcc/gcc/testsuite/gcc.dg/pragma-diag-10.c

 10 #pragma GCC diagnostic push
 11 #pragma GCC diagnostic ignored "-Wstringop-overflow"
 12 #pragma GCC diagnostic ignored "-Wstringop-overread"
 13   if (c != 0)
 14     return __builtin_memchr (s, c, (unsigned long)-1);
 15 #pragma GCC diagnostic pop

it's totally same as this PATCH.

I think the motivation for this patch is to eliminate the compilation
warning, maybe one day we will compile the kernel with "-Werror -Wall",
at which point this compilation warning will turn into a compilation
error, and in case we already know it, we should fix this error in
advance.

For old gcc, we can add this?

 #pragma GCC diagnostic push
+#if __GNUC__ >= 11 && __GNUC_MINOR__ >= 1
 /* Ignore read(2) overflow and write(2) overread compile warnings */
 #pragma GCC diagnostic ignored "-Wstringop-overread"
 #pragma GCC diagnostic ignored "-Wstringop-overflow"
+#endif

What do you think?

Good day!
Rong Tao