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Date: Wed, 12 Jul 2017 10:45:46 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: mkdir(2) prefers EACCES over EEXIST
Message-ID: <20170712084546.GF30071@calimero.vinschen.de>
Reply-To: cygwin AT cygwin DOT com
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References: <20170712011209 DOT GK17540 AT nullprogram DOT com>
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On Jul 11 21:12, Christopher Wellons wrote:
> This isn't _really_ a bug, more of an oddity. Calling mkdir(2) on an
> existing directory will fail with EACCES instead of EEXIST if the directo=
ry
> couldn't have been created in the first place. For example, this is the
> typical situation for /cygdrive/c:
>=20
>    mkdir("/cygdrive/c", 0700);
>    // errno =3D=3D EACCES
>=20
> Or from the shell:
>=20
>    $ mkdir /cygdrive/c
>    mkdir: cannot create directory =E2=80=98/cygdrive/c=E2=80=99: Permissi=
on denied
>=20
> Compare that to Linux or *BSD (giving EEXIST):
>=20
>    $ mkdir /etc
>    mkdir: cannot create directory =E2=80=98/etc=E2=80=99: File exists
>=20
>    $ mkdir /etc
>    mkdir: /etc: File exists
>=20
> This behavior seems to be permitted by POSIX =E2=80=94 both are valid rea=
sons for
> this system call to fail =E2=80=94 but it's a surprising result. I'd expe=
ct
> existence to take priority.

That's a result of calling the Windows function without prior check for
existence.  The Windows function apparently prefers it's variation of
EACCES over EEXIST, *iff* the target of the function is a drive.

I don't think it's worth to add a check to mkdir for such a border
case, just to prefer one error code over another.


Corinna

--=20
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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