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Date: Fri, 08 Feb 2013 20:53:51 +0100
From: Jens Gustedt <>
Subject: Re: guard bug for strerror_r


Am Freitag, den 08.02.2013, 13:59 -0500 schrieb Rich Felker:
> > #if defined(__GLIBC__) && defined(__USE_GNU)

the __GLIBC__ thing seems to work for my case, now. strerror_r seems
to be the only interface where they use the same name with a different
interface, so I'll bug something around that.

> I would simply avoid _ever_ using strerror_r on GNU systems. On any
> modern GNU or POSIX 2008 conforming system, you have the vastly
> superior strerror_l function. It does not require you to provide a
> buffer, and it's thread-safe (the buffer returned is either immutable
> static or thread-local). The logic I'd recommend is:
> #if _POSIX_VERSION >= 200809L || defined(__GLIBC__)
> /* use strerror_l */
> #else
> /* use strerror_r and assume POSIX version of it */
> #endif

Hm, I have a relatively recent system (ubuntu) and there is no trace
of strerror_l in the documentation, even in their "POSIX" man page.

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

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.


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