linux-kernel - Re: [PATCH v2] vsprintf: introduce %dE for error constants

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Message-ID: <7eb732b3-eca5-34c0-ed1f-6814deab60d9@rasmusvillemoes.dk>
Date:   Fri, 30 Aug 2019 23:45:42 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Uwe Kleine-König <uwe@...ine-koenig.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Juergen Gross <jgross@...e.com>, Petr Mladek <pmladek@...e.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Jonathan Corbet <corbet@....net>,
        metux IT consult Enrico Weigelt <lkml@...ux.net>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] vsprintf: introduce %dE for error constants

On 29/08/2019 19.39, Uwe Kleine-König wrote:
> On 8/29/19 11:09 AM, Rasmus Villemoes wrote:

>> still prefer making it %pE, both because it's easier to convert integers
>> to ERR_PTRs than having to worry about the type of PTR_ERR() being long
>> and not int, and because alphanumerics after %p have been ignored for a
>> long time (10 years?) whether or not those characters have been
>> recognized as a %p extension, so nobody relies on %pE putting an E after
>> the %p output. It also keeps the non-standard extensions in the same
>> "namespace", so to speak.
>>
>> Oh, 'E' is taken, well, make it 'e' then.
> 
> I like having %pe to print error valued pointers. Then maybe we could
> have both %de for ints and %pe for pointers. :-)

Oh no. And actually, come to think of it, we don't even need to extend
%p at all (taking away yet another letter for future expansion...), we
should simply make %p DTRT when passed an ERR_PTR - currently, if it's
some %p<extension> that would normally derefence it, there's sanity
checking in place which makes it print (efault), while if it's plain %p,
it just does the hashing, making it impossible to figure out that it was
an errno value (or which it was).

I've cooked up what I mean, sending in separate thread.

Rasmus