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Date: Fri, 08 Apr 2016 10:10:10 +0300
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From: "Eli Zaretskii (eliz AT gnu DOT org) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
To: djgpp AT delorie DOT com
In-reply-to: <5706E3D9.9070401@gmx.de> (djgpp@delorie.com)
Subject: Re: Different dup2 behaviour between DOS/DJGPP and posix.
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> Date: Fri, 08 Apr 2016 00:48:57 +0200
> From: "Juan Manuel Guerrero (juan DOT guerrero AT gmx DOT de) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
> 
> OK I think I have got it.  It is a bug in the DJGPP implementation of dup2.
> According to http://pubs.opengroup.org/onlinepubs/009695399/functions/dup.html
> The dup2() function shall fail if:
> 
> [EBADF]
>      The fildes argument is not a valid open file descriptor or the argument fildes2 is negative or greater than or equal to {OPEN_MAX}.
> 
> 
> The current implementation checks first if fd == newfd and if this is the case
> it returns inmediatly with newfd.  Here some fix will be required because no one
> of the 3 conditions are checked.  May be these error conditions were not in effect
> in those days when dup2 was implemented.

Yes, Posix has changed in this regard, AFAIR.