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

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Date:   Wed, 28 Aug 2019 14:49:15 +0200
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Uwe Kleine-König <uwe@...ine-koenig.org>,
        Steven Rostedt <rostedt@...dmis.org>, Enrico@...ine-koenig.org,
        Weigelt@...ine-koenig.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        metux IT consult <lkml@...ux.net>,
        Jonathan Corbet <corbet@....net>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] vsprintf: introduce %dE for error constants

On 28/08/2019 14.02, Sergey Senozhatsky wrote:
> On (08/28/19 14:54), Jani Nikula wrote:
> [..]
>>> I personally think that this feature is not worth the code, data,
>>> and bikeshedding.
>>
>> The obvious alternative, I think already mentioned, is to just add
>> strerror() or similar as a function. I doubt there'd be much opposition
>> to that. Folks could use %s and strerr(ret). And a follow-up could add
>> the special format specifier if needed.
> 
> Yeah, I'd say that strerror() would be a better alternative
> to vsprintf() specifier. (if we decide to add such functionality).

Please no. The .text footprint of the changes at the call sites to do
pr_err("...%s...", errcode(err)) instead of the current
pr_err("...%d...", err) would very soon dwarf whatever is necessary to
implement %pE or %dE. Also that would prevent any kind of graceful
fallback in case err doesn't have a known value - errcode() would have
to return some fixed "huh, unknown error number" string, so we'd lose
the actual number.

Rasmus