Re: dup2() vs dup3() inconsistency when

["H. Peter Anvin" <hpa@zytor.com>]

Ulrich Drepper wrote:
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> H. Peter Anvin wrote:
>> The result of dup3(fd, fd, O_CLOEXEC) is to set the O_CLOEXEC flag on fd.
> 
> That's bad and disregarded by Al and myself because it is one and the
> same descriptor and therefore it changes the source descriptor.

It's not the source descriptor, per se, it is the "new" descriptor, 
which happens to have a side effect of closing the "old" descriptor.

>> Step (2) could be considered a bit dubious, but the behaviour of
>> dup2(fd, fd) is a direct consequence of the chosen semantics.
> 
> The behavior of dup2(fd,fd) is just a result of an accident in the
> original implementation.  It makes no sense and the mistake doesn't have
> to be repeated.

Inconsistency is bad, too, and one could *definitely* argue that the 
fundamental problem is the one of closing a pre-existing descriptor 
rather than forcing the user to do that explicitly if that behaviour was 
desired.

	-hpa