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Message-ID: <4A0149FD.3010008@cn.fujitsu.com>
Date: Wed, 06 May 2009 16:27:41 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: Vegard Nossum <vegard.nossum@...il.com>
CC: Ingo Molnar <mingo@...e.hu>, Yinghai Lu <yinghai@...nel.org>,
Frederic Weisbecker <fweisbec@...il.com>,
Jeremy Fitzhardinge <jeremy@...p.org>,
Zhaolei <zhaolei@...fujitsu.com>, Li Zefan <lizf@...fujitsu.com>,
Steven Rostedt <rostedt@...dmis.org>,
Andrew Morton <akpm@...ux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: printk %0*X is broken.
Vegard Nossum wrote:
> 2009/5/6 Ingo Molnar <mingo@...e.hu>:
>> Cc:-ed more folks who modified lib/vsprintf.c recently.
>>
>> Ingo
>>
>> * Yinghai Lu <yinghai@...nel.org> wrote:
>>
>>> it seems someone broke
>>>
>>> printk( "%0*X\n", width, x);
>>>
>>> looks like 0 is dumped.
>
> After %, we look for flags. The problem is that when a flag is found, we
> don't advance in the format string. And thus we start looking for the
> precision, which is read as 0, because we are still at the 0. I think
> this patch should fix it.
>
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index 7536ace..ae7d4b2 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -800,14 +800,15 @@ static int format_decode(const char *fmt, struct printf_spec *spec)
> if (fmt != start || !*fmt)
> return fmt - start;
>
> + /* this skips the first '%' */
> + ++fmt;
> +
> /* Process flags */
> spec->flags = 0;
>
> - while (1) { /* this also skips first '%' */
> + while (1) {
> bool found = true;
>
> - ++fmt;
> -
> switch (*fmt) {
> case '-': spec->flags |= LEFT; break;
> case '+': spec->flags |= PLUS; break;
> @@ -819,6 +820,8 @@ static int format_decode(const char *fmt, struct printf_spec *spec)
>
> if (!found)
> break;
> +
> + ++fmt;
> }
>
It seems that your patch does not change anything.
The code logic is still the same as before.
Lai
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