Re: [PATCH] vsprintf: sanely handle NULL passed to %pe

From: Ilya Dryomov <idryomov@gmail.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Petr Mladek <pmladek@suse.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
	Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Kees Cook <keescook@chromium.org>,
	"Tobin C . Harding" <me@tobin.cc>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Linux Documentation List <linux-doc@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] vsprintf: sanely handle NULL passed to %pe
Date: Wed, 19 Feb 2020 12:29:59 +0100	[thread overview]
Message-ID: <CAOi1vP8e-RQ2DHFSDMBgod7Ug4yMMoJBwxGDYNXWA6UL68pixg@mail.gmail.com> (raw)
In-Reply-To: <CAHp75VeJm-hbbtVAu69ZbDCCjs9cUK922D=hhW-MVu5OxczDzg@mail.gmail.com>

On Wed, Feb 19, 2020 at 12:25 PM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
>
> On Wed, Feb 19, 2020 at 1:21 PM Ilya Dryomov <idryomov@gmail.com> wrote:
> > On Wed, Feb 19, 2020 at 9:21 AM Rasmus Villemoes
> > <linux@rasmusvillemoes.dk> wrote:
> > >
> > > Extend %pe to pretty-print NULL in addition to ERR_PTRs,
> > > i.e. everything IS_ERR_OR_NULL().
>
> ...
>
> > > +       [0] = "NULL",
>
> > > +       test("[NULL]", "[%pe]", NULL);
>
> > FWIW I was about to post a patch that just special cases NULL here.
> >
> > I think changing errname() to return "NULL" for 0 is overkill.
> > People will sooner or later discover that function and start using it
> > in contexts that don't have anything to do with pointers.  Returning
> > _some_ string for 0 (instead of NULL) makes it very close to standard
> > strerror(), and "NULL" for 0 (i.e. success) seems rather odd.
>
> %pe is specifically for _pointers_. I don't see a point in your comment.

%pe is for pointers, but errname() in lib/errname.c will likely grow
more users in the future.

Thanks,

                Ilya