linux-kernel - Re: printk %0*X is broken.

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Message-ID: <20090506161116.GA5997@nowhere>
Date:	Wed, 6 May 2009 18:11:19 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Li Zefan <lizf@...fujitsu.com>, Yinghai Lu <yinghai@...nel.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Jeremy Fitzhardinge <jeremy@...p.org>,
	Zhaolei <zhaolei@...fujitsu.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: printk %0*X is broken.

On Wed, May 06, 2009 at 04:30:21PM +0800, Li Zefan wrote:
> Ingo Molnar wrote:
> > 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.
> >>
> >> YH
> >>
> >> [    0.000000] MTRR variable ranges enabled:
> >> [    0.000000]   0 base 0   00000000 mask FF0 00000000 write-back
> >> [    0.000000]   1 base 10  00000000 mask FFF 80000000 write-back
> >> [    0.000000]   2 base 0   80000000 mask FFF 80000000 uncachable
> >> [    0.000000]   3 base 0   7F800000 mask FFF FF800000 uncachable
> >>
> 
> 2.6.30-rc4-tip, the output of my box:
> 
> high_width: 1
> MTRR variable ranges enabled:
>   0 base 000000000 mask FC0000000 write-back
>   1 base 03C000000 mask FFC000000 uncachable
>   2 base 0D0000000 mask FF8000000 write-combining
> 
> Is it possible that high_width is negative in your output?
> If high_width == -3, we can get exactly the same output with yours.


Indeed, a negative value given as the width will actually pad to the
right (reverse width forcing).
If you have -3, that matches the normal printf behaviour.

Yinghai, could you check please if that's the case for you? 

Thanks,

Frederic.

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