From: "Uwe Kleine-König" <uwe@kleine-koenig.org>
To: Rasmus Villemoes <linux@rasmusvillemoes.dk>,
Joe Perches <joe@perches.com>,
Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Jonathan Corbet <corbet@lwn.net>, Petr Mladek <pmladek@suse.com>,
Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
Jani Nikula <jani.nikula@linux.intel.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Documentation List <linux-doc@vger.kernel.org>
Subject: Re: [PATCH v2] printf: add support for printing symbolic error codes
Date: Wed, 11 Sep 2019 11:37:28 +0200 [thread overview]
Message-ID: <8f21cddf-0e39-8379-6eab-60e8238a020d@kleine-koenig.org> (raw)
In-Reply-To: <354dc1f5-45b8-9e51-1ba0-b1fd368be45a@rasmusvillemoes.dk>
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On 9/11/19 8:43 AM, Rasmus Villemoes wrote:
> On 11/09/2019 02.15, Joe Perches wrote:
>> On Tue, 2019-09-10 at 18:26 +0300, Andy Shevchenko wrote:
>>> On Mon, Sep 9, 2019 at 11:39 PM Rasmus Villemoes
>>> <linux@rasmusvillemoes.dk> wrote:
>
>>>> +#define E(err) [err + BUILD_BUG_ON_ZERO(err <= 0 || err > 300)] = #err
>>>> +#define E(err) [err - 512 + BUILD_BUG_ON_ZERO(err < 512 || err > 550)] = #err
>>>
>>> From long term prospective 300 and 550 hard coded here may be forgotten.
>
> No? The point of the BUILD_BUG_ON_ZEROs is that if you add a new
> Esomething, you'll get an instant build error if Esomething doesn't fit
> nicely in the array you put it in. Then one can go back and figure out
> whether the limit should be raised, a new codes_foo should be created,
> or if it's early enough so it's not ABI yet, simply change Esomething to
> a saner value.
>
> A much bigger problem is that it's possible to add something to some
> errno.h without updating this table, but there's no good solution for
> that, I'm afraid. However, new Esomething are very rarely added, and
> printf() will still handle it gracefully until somebody notices.
>
>>>> +const char *errcode(int err)
>>> We got long, why not to use long type for it?
>
> Because errno values by definition have type int - and the linux syscall
> ABI very clearly limits values to [1,4095]. I can change the type used
> in vsnprintf.c if you prefer.
>
>>>> +{
>>>> + /* Might as well accept both -EIO and EIO. */
>>>> + if (err < 0)
>>>> + err = -err;
>>>> + if (err <= 0) /* INT_MIN or 0 */
>>>> + return NULL;
>>>> + if (err < ARRAY_SIZE(codes_0))
>>>> + return codes_0[err];
>>>
>>> It won't work if one of the #ifdef:s in the array fails.
>>> Would it?
>
> I don't understand what you mean. How can an ifdef fail(?), and what
> exactly won't work?
I think Joe means: What happens if codes_0[57] is "" because there is no
ESOMETHING with value 57.
Best regards
Uwe
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next prev parent reply other threads:[~2019-09-11 9:37 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-30 21:46 [PATCH] printf: add support for printing symbolic error codes Rasmus Villemoes
2019-08-30 21:53 ` Joe Perches
2019-08-30 22:03 ` Rasmus Villemoes
2019-08-30 22:21 ` Joe Perches
2019-08-30 22:50 ` Rasmus Villemoes
2019-09-02 9:07 ` David Laight
2019-08-31 9:38 ` kbuild test robot
2019-09-02 15:29 ` Uwe Kleine-König
2019-09-04 9:13 ` Rasmus Villemoes
2019-09-04 9:21 ` Uwe Kleine-König
2019-09-04 16:19 ` Andy Shevchenko
2019-09-04 16:28 ` Uwe Kleine-König
2019-09-05 11:40 ` Rasmus Villemoes
2019-09-09 20:38 ` [PATCH v2] " Rasmus Villemoes
2019-09-10 15:26 ` Andy Shevchenko
2019-09-11 0:15 ` Joe Perches
2019-09-11 6:43 ` Rasmus Villemoes
2019-09-11 9:37 ` Uwe Kleine-König [this message]
2019-09-11 10:14 ` Rasmus Villemoes
2019-09-15 9:43 ` Pavel Machek
2019-09-16 12:23 ` Uwe Kleine-König
2019-09-16 13:23 ` Rasmus Villemoes
2019-09-16 13:36 ` Uwe Kleine-König
2019-09-17 6:59 ` [PATCH v3] " Rasmus Villemoes
2019-09-25 14:36 ` Petr Mladek
2019-09-29 20:09 ` Rasmus Villemoes
2019-10-02 8:34 ` Petr Mladek
2019-10-05 21:48 ` Andrew Morton
2019-10-11 13:36 ` [PATCH v4 0/1] printf: add support for printing symbolic error names Rasmus Villemoes
2019-10-11 13:36 ` [PATCH v4 1/1] " Rasmus Villemoes
2019-10-14 5:51 ` Uwe Kleine-König
2019-10-14 13:02 ` Petr Mladek
2019-10-14 13:10 ` Andy Shevchenko
2019-10-15 12:17 ` Rasmus Villemoes
2019-10-15 13:44 ` David Laight
2019-10-15 19:07 ` [PATCH v5] " Rasmus Villemoes
2019-10-16 13:49 ` Andy Shevchenko
2019-10-16 14:52 ` Petr Mladek
2019-10-16 16:31 ` Andy Shevchenko
2019-10-17 15:02 ` Petr Mladek
2019-11-26 14:04 ` [PATCH v4 0/1] " Geert Uytterhoeven
2019-11-27 8:54 ` Petr Mladek
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