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

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Message-ID: <20190828125951.GA12653@jagdpanzerIV>
Date:   Wed, 28 Aug 2019 21:59:51 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Rasmus Villemoes <linux@...musvillemoes.dk>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        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 (08/28/19 14:49), Rasmus Villemoes wrote:
> 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.

New vsprintf() specifiers have some downsides as well. Should %dE
accidentally (via backport) make it to the -stable kernel, which
does not support %dE, and we are going to lose the actual error
code value as well.

	-ss