linux-kernel - RE: [PATCH v4 1/1] printf: add support for printing symbolic error names

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Message-ID: <904b85b3c32d448abc6b4e58b6c4dc35@AcuMS.aculab.com>
Date:   Tue, 15 Oct 2019 13:44:30 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Petr Mladek' <pmladek@...e.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
CC:     Uwe Kleine-König <uwe@...ine-koenig.org>,
        Joe Perches <joe@...ches.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH v4 1/1] printf: add support for printing symbolic error
 names

From: Petr Mladek
> Sent: 14 October 2019 14:03
> On Fri 2019-10-11 15:36:17, Rasmus Villemoes wrote:
> > It has been suggested several times to extend vsnprintf() to be able
> > to convert the numeric value of ENOSPC to print "ENOSPC". This
> > implements that as a %p extension: With %pe, one can do
> 
> Reviewed-by: Petr Mladek <pmladek@...e.com>
> 
> I like the patch. There are only two rather cosmetic things.
> 
> > diff --git a/lib/errname.c b/lib/errname.c
> > new file mode 100644
> > index 000000000000..30d3bab99477
> > --- /dev/null
> > +++ b/lib/errname.c
> > +const char *errname(int err)
> > +{
> > +	bool pos = err > 0;
> > +	const char *name = __errname(err > 0 ? err : -err);
> > +
> > +	return name ? name + pos : NULL;
> 
> This made me to check C standard. It seems that "true" really has
> to be "1".

What is thus "true" symbol you are talking about?
Actually you could get rid of the "bool" as well.
	unsigned int pos = err > 0;
	const char *name = __errname(pos ? err : -err);
	return name ? &pos[name] : NULL;
then it is all well defined.

	David

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