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Date: Fri, 08 Feb 2013 21:31:11 +0100
From: Jens Gustedt <>
Subject: Re: guard bug for strerror_r

Am Freitag, den 08.02.2013, 15:01 -0500 schrieb Rich Felker:
> It's part of the "xlocale" set of interfaces that seem to have
> originated with glibc or maybe Sun, and later made it into POSIX 2008.
> It allows you to pass a locale_t argument to get the results in a
> non-default locale, but you can instead just request the current
> locale.

really bizarre that they didn't estimate it necessary to document it

> > And I actually use this in P99 to provide the C11 Annex K interface
> > strerror_s, which is much closer to strerror_r than strerror_l. Well,
> > we now have
> Are you sure this is the best interface to provide to applications?

the best I don't know, but it is now a standard and provides
runtime-constraint handlers, and basic function parameter checking,
which are nice features. (Just forget about the official title "Bounds
checking interfaces".)

> I'd instead provide a thread-safe interface with an interface
> identical to strerror, since that's by far the easiest to use.
> If on the other hand you want to provide Annex K in principle,

I do

> that's
> another matter, but there's a fairly large portion of it that can't be
> provided portably on top of an existing libc (mainly the scanf or
> printf stuff, I think).

yes, these don't work and since P99 isn't a library but only wrappers
I can't provide that. But for the most of it the wrappers are quite
simple and provided by P99.

> > strerror    C, POSIX
> > strerror_r  POSIX
> > strerror_l  POSIX
> > strerror_s  C
> > 
> > superbe. Again a case where a liaison between the C committee and the
> > POSIX could have helped.
> The problem seems to be just that C didn't have threads (and thus no
> need for strerror_r or strerror_l) until C11.

But now they have threads, and so at the same moment of introducing
them they could have equipped them with a semantic (POSIX comes into
mind :) and used other interfaces from POSIX that already exist.

And, also I think that even before the _r version would have been a
good thing. I think the _r stands for reentrant, and for a function
that you would typically like to use in error or signal handlers, this
is a nice feature.


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