linux-kernel - RE: [RFC] vsprintf: compile error on %09pK

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Date:   Tue, 04 Apr 2023 19:16:06 +0900
From:   Jaewon Kim <jaewon31.kim@...sung.com>
To:     Sergey Senozhatsky <senozhatsky@...omium.org>,
        Jaewon Kim <jaewon31.kim@...il.com>
CC:     Petr Mladek <pmladek@...e.com>,
        Jaewon Kim <jaewon31.kim@...sung.com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        GyeongHwan Hong <gh21.hong@...sung.com>
Subject: RE: [RFC] vsprintf: compile error on %09pK

>[..]
>> 
>> Okay, then we can't use %09pK. I've just wondered because %9pK works.
>
>This is not per printk / kernel, Wformat warnings come from the
>compiler.
>
>Per C11 (7.21.6 6):
> 0  For d, i, o, u, x, X, a, A, e, E, f, F, g, and G conversions, leading zeros
>    (following any indication of sign or base) are used to pad to the field width
>    rather than performing space padding
>    ...
>    For other conversions, the behavior is undefined.
>
>So using 0 for p should trigger an undefined behavior as far as the
>standard C concerned. Unless I'm missing something.

Thank your for the information about the leading 0 case. By the way do you know
if there is policy for none 0 digit like %9pK?

Jaewon Kim