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Date: Wed, 28 Aug 2019 16:22:20 +0200
From: Corinna Vinschen <corinna-cygwin AT cygwin DOT com>
To: Eric Blake <eblake AT redhat DOT com>
Cc: cygwin AT cygwin DOT com
Subject: Re: Odd, is it not? mkdir 'e:\' cannot be undone by rmdir 'e:\' ...
Message-ID: <20190828142220.GN11632@calimero.vinschen.de>
Reply-To: cygwin AT cygwin DOT com
Mail-Followup-To: Eric Blake <eblake AT redhat DOT com>, cygwin AT cygwin DOT com
References: <bc3df101ab93c20b86c3ab7fa7d3ea4f AT xs4all DOT nl> <20190827152549 DOT GY11632 AT calimero DOT vinschen DOT de> <a47cc167b725c08e6f1c914166fabcaf AT smtp-cloud8 DOT xs4all DOT net> <3E262D05-F393-453A-9E43-B248DDE50812 AT solidrocksystems DOT com> <b97e4dbe952154efc68412540514ae81 AT smtp-cloud8 DOT xs4all DOT net> <20190828125939 DOT GL11632 AT calimero DOT vinschen DOT de> <421ac447-b249-da21-1ca5-228041cfc884 AT redhat DOT com> <20190828141556 DOT GM11632 AT calimero DOT vinschen DOT de>
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On Aug 28 16:15, Corinna Vinschen wrote:
> On Aug 28 08:36, Eric Blake wrote:
> > On 8/28/19 7:59 AM, Corinna Vinschen wrote:
> >=20
> > >>>>> mkdir(2) has some special code from 2009 which drops trailing
> > >>>>> {back}slashes to perform a bordercase in mkdir Linux-compatible.
> > >>>>> This code snippet doesn't exist in rmdir(2).
> >=20
> > Dropping trailing slashes to be Linux-compatible is okay.  Dropping
> > trailing backslashes is risky, though, if it makes us forget that the
> > user was asking for a DOS path (even though DOS paths are not always
> > going to work as expected).
> >=20
> >=20
> > >=20
> > > Eric, any insight?  As usual our comments from way back when are lack=
ing
> > > in terms of what exact problem this code is trying to fix/workaround.
> >=20
> > If I recall, we had cases where 'mkdir a/' and 'mkdir a' did not behave
> > identically, even though POSIX says they should; compounded by the fact
> > that Windows treats trailing slash differently when performing native
> > mkdir on a drive than it does on a subdirectory of a drive.
> >=20
> > It may be as simple as changing the isdirsep() from the identified
> > commit to instead check only for '/' (and ignore '\').
>=20
> As simple as that?
>=20
> diff --git a/winsup/cygwin/dir.cc b/winsup/cygwin/dir.cc
> index b757851d5c7f..747b1582af50 100644
> --- a/winsup/cygwin/dir.cc
> +++ b/winsup/cygwin/dir.cc
> @@ -314,13 +314,13 @@ mkdir (const char *dir, mode_t mode)
>  	  set_errno (ENOENT);
>  	  __leave;
>  	}
> -      if (isdirsep (dir[strlen (dir) - 1]))
> +      if (dir[strlen (dir) - 1] =3D=3D '/')
>  	{
>  	  /* This converts // to /, but since both give EEXIST, we're okay.  */
>  	  char *buf;
>  	  char *p =3D stpcpy (buf =3D tp.c_get (), dir) - 1;
>  	  dir =3D buf;
> -	  while (p > dir && isdirsep (*p))
> +	  while (p > dir && *p =3D=3D '/')
>  	    *p-- =3D '\0';
>  	}
>        if (!(fh =3D build_fh_name (dir, PC_SYM_NOFOLLOW)))

One problem here is, what to do about border cases like

  $ mkdir a\/\/\/

In theory slashes and backslashes should both be treated as dir
separators.  Handling a case like this so that all expectations
are satisfied is next to impossible, I guess.


Corinna

--=20
Corinna Vinschen
Cygwin Maintainer

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