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b=C9id5lYjK92n5sZ/VTqlQbGQctviZIqwCK1nGi3B5hj2XxbSzzg9Jjk5VBhM08L63 yGG34m6wGabcqhIO/0rs1SI8NDY5MD54ArcRXrgKPOrCWbcbZiSoPW9EPMNsRm9eZK LaBkOwQ1o5ydbMLsJdPuLIpOrJkAGrfp2622cW0s6iZWDp/yDa+0AllA953/b1/uLY D9mB14Bf3pPjSl9HdjhodKzpwvDt68SZdCRhY8qVX5FGi+6w1Aqrg3VjqHYm+7+G7D tY6uqbDGbtZV6ysFwr/tOPnKPRavrXwnfg5DDyk2BjEiaH/lLj2qFXdlnD1v0umAYS L9EhlrvSjjiJg== Date: Mon, 7 Oct 2024 17:51:36 -0700 From: Nathan Chancellor To: Aleksei Vetrov Cc: Shivamurthy Shastri , linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, vbabka@suse.cz, willy@infradead.org, hannes@cmpxchg.org, anna-maria@linutronix.de, tglx@linutronix.de, arnd@arndb.de, llvm@lists.linux.dev Subject: Re: [PATCH] mm/vmstat: Fix -Wenum-enum-conversion warning in vmstat.h Message-ID: <20241008005136.GA241099@thelio-3990X> References: <20240621111604.25330-1-shivamurthy.shastri@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Stat-Signature: 89krfg7yzmsrgqck6ym6mg3nicgtq185 X-Rspamd-Queue-Id: 6E0AE8000D X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1728348699-957864 X-HE-Meta: U2FsdGVkX18XdS0TuqzzWZ5CagOnYMDdsWVepoQ3JqiPG+LF3ajOMbiSwSOHPW0zV7R8nUxXdrGpwkqEJC7aogesxcca85M/GtblbxoAyB4tjK3mnrwKFFgb/FIjBP9vPMeG6yqLowp0+mXD0cOkStpa+3WKH5+qt04ZbrTdnzHqt0fZC/PI5aL/fdGkD+uNw/28lX4bKBdVpTdYaDRkAkDGyIdLIzsK6UAVKg11KHncW//Tb7krcgxI1396kSvAaKZe2AQNCHS3Ab4rA04V/f8meZqVOnEkz2SnBecMWCaHYQ6rrsxUPENmYpzUpl96J16nsbpnnSGuLwQKzJzEg8LvhVNeBITxyErOAeqjH/RivJRQzlEEjyyZHI24+jyFRWxcuBLcPxbZLhm5ctf770E5ZCpToCtgEKCcaxM6YbKt4Y9IVVsEi0wNnabx582CgmC6nB76JnZyHOxRXrvvITSAw3n+TFnu/eB/oRNx5dQLS/gX3xOadQd7oOuPH60On+GSuHVDy6GgYvQxZRoxj6DATx3XKmWyLqDhSGrJ2WZh0O2BSivdHDdWKZMXPx1VhIt7X4m2EvdUUtlsJ8uJuFgG+c1JrN485KOKw9/aiD2GxNohdo9bkU5nwSsV43oYGhkl43AlV2nbqz7RCTGzYg1Z8UxT0ln48Nngo5jG99WhGRorEpWrtnhjoanxuAcAmCoJjfM/ZM2mIBORxFS33DCcKXf2+acBMuu1QXUErlbl+AgoufoC9DMZWcokdJcN76n8JacYwE0HkK4pL0V6DtKYio6b+7kfY9FACojcqyX/mLX1NekTDp4m8KHbyaAVkmtE6JrCfJq5jlhm7oWXthWZsB7yHI4tuKYdVYCPwrHbQmLAWngiWm6vyTB6c1icn+0nnw8RO57ZV9vgXor8gy96jxU7v7XERPHeTtEZzjG029t8zo377DQTQYumC8/0OiC6vqJgmIoOdBDyRQj J52kIcSG 3ccYrCCjpInn8Z1CY6K/91rgK75P9HS9+ZH2H/jTPCw5rS5DEWzF0HbB1cYG4DuRPiswo4lCdCNc62X5IbsQbgThf3o721uJq+Ulzd2yc60yyWkvc1Jgz0JIV/1G2G9YiYZ/kP06FPbXUS+WIMpY3w8F/oe0r1LE8J/4aae0VGSgPgheD6RrNvJGf7/QiD1zyGMDADo1PkLE6qgJ41oTYfesmhyEU2FiSLNjqNpOFuM7vDjzNCpGUUmHpb6CiXqGer9Erdex0UBE01aYirHe1sLQqS8O3iQO5V6oCrAvXF7KX4tA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Aleksei, On Mon, Oct 07, 2024 at 08:13:41PM +0000, Aleksei Vetrov wrote: > Hi Shivamurthy, > > On Fri, Jun 21, 2024 at 01:16:04PM +0200, Shivamurthy Shastri wrote: > > A W=1 build with -Wenum-enum-conversion enabled, results in the > > following build warning due to an arithmetic operation between different > > enumeration types 'enum node_stat_item' and 'enum lru_list': > > > > include/linux/vmstat.h:514:36: warning: arithmetic between different enumeration types ('enum node_stat_item' and 'enum lru_list') [-Wenum-enum-conversion] > > 514 | return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_" > > | ~~~~~~~~~~~ ^ ~~~ > > > > Address this by casting lru to the proper type. > > > > Signed-off-by: Shivamurthy Shastri > > Reviewed-by: Anna-Maria Behnsen > > --- > > include/linux/vmstat.h | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h > > index 735eae6e272c..72ecd46fd0c4 100644 > > --- a/include/linux/vmstat.h > > +++ b/include/linux/vmstat.h > > @@ -511,7 +511,7 @@ static inline const char *node_stat_name(enum node_stat_item item) > > > > static inline const char *lru_list_name(enum lru_list lru) > > { > > - return node_stat_name(NR_LRU_BASE + lru) + 3; // skip "nr_" > > + return node_stat_name(NR_LRU_BASE + (enum node_stat_item)lru) + 3; // skip "nr_" > > } > > > > static inline const char *writeback_stat_name(enum writeback_stat_item item) > > -- > > 2.34.1 > > > > We have encountered the same problem after trying to update Clang to the > latest version and this is a blocker because we use W=1 to compile the > kernel. > > Do you plan to address review comments about casting to int instead of > enum node_stat_item? Or I can submit another patch myself that addresses > it. For what it's worth, I never really saw Matthew's comment around what value does this warning provide addressed. I was the one who originally moved it into W=1 at the request of Arnd because he felt that instances of this warning could be bugs and they should be audited. However, I have not seen many instances of this warning pop up in new code through 0day build reports and the ones that I have seen seem to be intentional, as they are using enums like integral values, such as here. If that is just going to result in a bunch of patches like this adding unnecessary casts, I think it would just be better to consider disabling this warning altogether or at the very least, moving it to W=2 (which is for warnings that are noisy but might contain bugs), since more people are using W=1 as their normal build configuration nowadays. Cheers, Nathan