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Date: Wed, 07 Mar 2012 20:20:00 +0200
From: Eli Zaretskii <eliz AT gnu DOT org>
Subject: Re: errno returned by open()
In-reply-to: <201203071845.09240.juan.guerrero@gmx.de>
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> From: Juan Manuel Guerrero <juan DOT guerrero AT gmx DOT de>
> Date: Wed, 7 Mar 2012 18:45:09 +0100
> 
>    if (fd == -1)
>      return fd;	/* errno already set by _open or _creat */
> +  else
> +    errno = 0;  /* at this stage reset errno set by
> +                   previous calls to _open or _creat */

This isn't right.  If a function succeeds, it should leave errno at
the same value as it was when the function was called.  Forcing it to
zero is not TRT when some previous code set errno to something
non-zero.

What you need is to save the value of errno upon entry to `open', and
then restore it on successful exit.

Thanks.