linux-kernel - Re: [PATCH 5/5] lib: Add error string support to printks

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Message-ID: <22238.1379502295@warthog.procyon.org.uk>
Date:	Wed, 18 Sep 2013 12:04:55 +0100
From:	David Howells <dhowells@...hat.com>
To:	Joe Perches <joe@...ches.com>
Cc:	dhowells@...hat.com, Daniel Santos <daniel.santos@...ox.com>,
	linux-kbuild <linux-kbuild@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Michal Marek <mmarek@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Michael Kerrisk <mtk.manpages@...il.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	George Spelvin <linux@...izon.com>
Subject: Re: [PATCH 5/5] lib: Add error string support to printks

Joe Perches <joe@...ches.com> wrote:

> On Tue, 2013-09-17 at 18:08 -0500, danielfsantos@....net wrote:
> > This adds an extension for the integral format specifier suffix of 'e',
> > so that the format %[duxXo]e will result in printing an number (as
> > before) in addition to a name and descrption for an error code, if such
> > support is enabled and a name and descrption is found.
> > 
> > My initial thought was to use the glibc extension of '%m', but this
> > format specifier uses the value of libc's errno and adding a value
> > breaks gcc's printf parsing.  I'm not convinced that the 'e' extension
> > is optimal, although there are only four instances of this pattern in
> > the kernel that would need to be changed.
> > 
> >     git grep -E '".*%[#0\ +\-]*[0-9]*[hljzt]*[idoxXu]e'
> > 
> > Alternatively, 'E' was another thought for a suffix as well.
> 
> I'd much rather see another %p extension used instead
> of generating odd output given normal printf formats.
> 
> %pE might work

I guess you'd use that with ERR_PTR().  On one hand, it would look decidedly
odd, but on the other hand, we have errors in pointers in a lot of places
already which wouldn't then need converting back - so it doesn't seem entirely
unreasonable.

David
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