From: "H. Peter Anvin" <hpa@zytor.com>
To: David Desobry <david.desobry@formalgen.com>,
David Laight <david.laight.linux@gmail.com>
Cc: tglx@kernel.org, mingo@redhat.com, bp@alien8.de,
dave.hansen@linux.intel.com, x86@kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] x86/lib: Optimize num_digits() and fix INT_MIN overflow
Date: Tue, 20 Jan 2026 16:17:52 -0800 [thread overview]
Message-ID: <02817c9a-e512-427f-bd64-b1420132adf6@zytor.com> (raw)
In-Reply-To: <ef852c16-3736-4bd5-bc65-69211b05506e@formalgen.com>
On 2026-01-20 16:04, David Desobry wrote:
>
> Actually, the V3 change:
> if (val < 0) {
> - d++;
> - val = -val;
> + d = 1;
> + v = -val;
> + } else {
> + d = 0;
> + v = val;
> }
> reintroduced the undefined behavior for val == INT_MIN.
> So this V3 version is incorrect.
> I'm not familiar enough with the rest of the codebase to know if changing the
> function signature to unsigned int is correct here.
It is only ever called with a cpu number, a node number, or a CPU count. Never
negative.
-hpa
next prev parent reply other threads:[~2026-01-21 0:18 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-01-20 17:47 David Desobry
2026-01-20 18:03 ` H. Peter Anvin
2026-01-20 21:46 ` David Laight
2026-01-20 23:19 ` [PATCH v3] " David Desobry
2026-01-20 23:32 ` [PATCH v2] " David Desobry
2026-01-20 23:49 ` H. Peter Anvin
2026-01-21 0:04 ` David Desobry
2026-01-21 0:17 ` H. Peter Anvin [this message]
2026-01-21 9:39 ` [PATCH v4] " David Desobry
2026-01-21 11:36 ` David Laight
2026-01-21 15:46 ` H. Peter Anvin
2026-01-21 9:54 ` [PATCH v2] " David Laight
2026-01-21 10:32 ` [PATCH v5] x86/lib: Rename num_digits() to num_digits_u32() and optimize David Desobry
2026-01-21 10:40 ` [PATCH v2] x86/lib: Optimize num_digits() and fix INT_MIN overflow David Desobry
2026-01-21 11:51 ` Maciej W. Rozycki
2026-01-23 7:06 ` H. Peter Anvin
2026-01-23 10:55 ` Maciej W. Rozycki
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