linux-kernel - Re: [PATCH 4/5 v2] x86 boot: show pfn addresses in hex not decimal in some kernel info printks

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Message-ID: <alpine.LFD.1.10.0806241949030.13106@hp.linux-foundation.org>
Date:	Tue, 24 Jun 2008 19:58:36 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	"H. Peter Anvin" <hpa@...or.com>
cc:	Paul Jackson <pj@....com>, yhlu.kernel@...il.com,
	akpm@...ux-foundation.org, mingo@...e.hu, tglx@...utronix.de,
	steiner@....com, travis@....com, linux-kernel@...r.kernel.org,
	ying.huang@...el.com, andi@...stfloor.org
Subject: Re: [PATCH 4/5 v2] x86 boot: show pfn addresses in hex not decimal
 in some kernel info printks

On Tue, 24 Jun 2008, H. Peter Anvin wrote:
> 
> What we really should have is %p produce this format.  For some odd reason,
> right now %p produces numbers without the 0x prefix.

Actually, I'd like to make %p produce the format that you right now have 
to jump through insane hoops for: symbolic addresses.

Right now you have to do something insane like

	print_symbol(KERN_WARNING "address: %s\n", ptr);

to print a symbolic version, and it sucks because it's actually just able 
to print symbols, you cannot mix any other types in there.

I think it would be much easier to use if "%p" just did the symbolic 
version (if it's relevant) automatically. If you _just_ want the hex 
representation, you can already always just use %#lx and a cast.

(Of course, then for things that we can't make into symbolic names, we'd 
have to fall back to just the hex representation, and whether that one 
then includes the 0x or not I don't have strong opinions on.)

And yes, to avoid messing with current users, maybe we should only do that 
with %#p (which I don't think anybody uses right now, although I suspect 
it actually adds the '0x' you'd like). The '#' thing is, of course, all 
about 'alternate forms'. But I worry that gcc warns about undefined 
formatting behavior.

			Linus
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