linux-kernel - Re: [PATCH v2] x86/lib: Optimize num_digits() and fix INT

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Message-ID: <02817c9a-e512-427f-bd64-b1420132adf6@zytor.com>
Date: Tue, 20 Jan 2026 16:17:52 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: David Desobry <david.desobry@...malgen.com>,
        David Laight <david.laight.linux@...il.com>
Cc: tglx@...nel.org, mingo@...hat.com, bp@...en8.de,
        dave.hansen@...ux.intel.com, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] x86/lib: Optimize num_digits() and fix INT_MIN
 overflow

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