linux-kernel - Re: [PATCH] net: skbuff: use _RET_IP

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Message-ID: <1369977659.10556.34.camel@joe-AO722>
Date:	Thu, 30 May 2013 22:20:59 -0700
From:	Joe Perches <joe@...ches.com>
To:	Davidlohr Bueso <davidlohr.bueso@...com>
Cc:	Bjørn Mork <bjorn@...k.no>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] net: skbuff: use _RET_IP_

On Thu, 2013-05-30 at 18:11 -0700, Davidlohr Bueso wrote:
> On Thu, 2013-05-30 at 13:08 +0200, Bjørn Mork wrote:
> > Sergei Shtylyov <sergei.shtylyov@...entembedded.com> writes:
> > 
> > >     Why not "text:%#lx" as already used in this string? It's
> > > equivalent to "0x%lx".
> > 
> > Well, I don't know the reasoning in this case, but I'd like to note that
> > those are not strictly equivalent.  Personally I find the formatting of 0
> > annoying enough to avoid %#x for any value which may be 0.  It's
> > especially bad if you try to line up things by adding leading zeros.
> 
> Yep, I found that 0x%lx produced the same output as %p.

Don't use a standalone gcc compiled program to
determine what the kernel outputs.

lib/vsprintf.c does not output the same. (32 bit)

The kernel output is;

	printk("0x%lx\n", 0x100ul)		0x100
	printk("%p\n", (void *)0x100ul)		00000100
	printk("%#p\n", (void *)0x100ul)	0x00000100

The last one isn't used at all in kernel source. (gcc complains)
It's always "0x%p"

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