Date: Tue, 2 Dec 2008 13:08:40 +0100
From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: Avoid duplicate names in /proc/registry (which may crash find) 	?
Message-ID: <20081202120840.GM12905@calimero.vinschen.de>
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On Dec  1 21:16, Christian Franke wrote:
> When dirent.d_type support is added to /proc/registry (see attachment), 
> find 4.4.0-3 crashes on keys with duplicate names.
>
> Testcases:
>
> $ find-with-d_type \
> /proc/registry/HKEY_LOCAL_MACHINE/SOFTWARE/Microsoft/ALG/ISV
>
> $ find-with-d_type \
> /proc/registry/HKEY_LOCAL_MACHINE/SYSTEM/ControlSet001/Services/Eventlog/Security
>
> These keys contain a key and a value with the same name and readdir() 
> returns both (with different d_type).
>
> Possible fix to avoid identical names:
>
>
> 1. Put keys and values in different namespaces, e.g.
>
> /proc/registry/path/name.key
> /proc/registry/path/name.val
>
> Drawback: Breaks backward compatibility.
>
>
> or:
>
> 2. In readdir(), record the key names in some set<> or hash-table. If (and 
> only if) a duplicate name is detected, return a modified name for the 
> value:
>
> /proc/registry/path/name
> /proc/registry/path/name%76  ('v')
>
> Drawback: Slows down readdir, introduces alias name for value.

Some random thoughts:

- Do we really need d_type support in the registry?  How often is
  that actually used?

- If find crashes in this situation, isn't this a bug in find which
  should be fixed in find?

- /proc/registry is a convenience for reading the registry.  Due to some
  funny definitions of the registry it's not a full solution.  You can't
  write this way, you can't even access the "(Default)" key values.
  I personally don't worry if some border cases don't work.  For the
  border cases and for the full access we have regtool.

  Having said that, I really don't know what's the best solution for
  these problems would be.  None of the above ideas are very attractive.
  For instance, in idea 1, the path would actually be

    /proc/registry/HKEY_LOCAL_MACHINE.key/SOFTWARE.key/Cygwin.key/blub.val

  Shouldn't we rather defer these border cases to regtool?


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Project Co-Leader          cygwin AT cygwin DOT com
Red Hat

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