From: "Arnd Bergmann" <arnd@arndb.de>
To: "Dave Kleikamp" <dave.kleikamp@oracle.com>,
"Arnd Bergmann" <arnd@kernel.org>,
"Dave Kleikamp" <shaggy@kernel.org>,
"Nathan Chancellor" <nathan@kernel.org>,
"Zheng Yu" <zheng.yu@northwestern.edu>
Cc: "Nick Desaulniers" <nick.desaulniers+lkml@gmail.com>,
"Bill Wendling" <morbo@google.com>,
"Justin Stitt" <justinstitt@google.com>,
"Aditya Dutt" <duttaditya18@gmail.com>,
"Roman Smirnov" <r.smirnov@omp.ru>,
jfs-discussion@lists.sourceforge.net,
linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH] jfs: avoid -Wtautological-constant-out-of-range-compare warning
Date: Mon, 02 Feb 2026 21:44:08 +0100 [thread overview]
Message-ID: <38f05cd4-6844-481a-8293-3b87f9f1a9c6@app.fastmail.com> (raw)
In-Reply-To: <fd1854c2-d3f1-4901-8b7d-c6ce944caf61@oracle.com>
On Mon, Feb 2, 2026, at 18:34, Dave Kleikamp wrote:
> On 2/2/26 3:49AM, Arnd Bergmann wrote:
>> From: Arnd Bergmann <arnd@arndb.de>
>>
>> A recent change for the range check started triggering a clang warning:
>>
>> fs/jfs/jfs_dtree.c:2906:31: error: result of comparison of constant 128 with expression of type 's8' (aka 'signed char') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
>> 2906 | if (stbl[i] < 0 || stbl[i] >= DTPAGEMAXSLOT) {
>> | ~~~~~~~ ^ ~~~~~~~~~~~~~
>> fs/jfs/jfs_dtree.c:3111:30: error: result of comparison of constant 128 with expression of type 's8' (aka 'signed char') is always false [-Werror,-Wtautological-constant-out-of-range-compare]
>> 3111 | if (stbl[0] < 0 || stbl[0] >= DTPAGEMAXSLOT) {
>> | ~~~~~~~ ^ ~~~~~~~~~~~~~
>>
>> Both the old and the new check were useless, but the previous version
>> apparently did not lead to the warning.
>>
>> Rephrase this again by adding a cast. The check is still always false,
>> but the compiler shuts up about it.
>
> I think it would be better to just drop the useless part of these tests.
Fair enough, sent v2 now.
Arnd
prev parent reply other threads:[~2026-02-02 20:44 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-02 9:49 Arnd Bergmann
2026-02-02 17:34 ` Dave Kleikamp
2026-02-02 20:44 ` Arnd Bergmann [this message]
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