Re: [Fwd: symboilc link does not expand if followed by /..]

[Christopher Faylor <me at cgf dot cx>]

On Wed, Jul 14, 2004 at 01:55:55PM +0200, Corinna Vinschen wrote:
>----- Forwarded message from Vinay Kumar -----
>> Date: Tue, 13 Jul 2004 21:06:08 +0000 (GMT)
>> From: Vinay Kumar 
>> Subject: symboilc link does not expand if followed by /..
>> To: cygwin-list
>> 
>> Hi all,
>>     I found a problem with symbolic link expansion in cygwin. Symbolic
>> link does not expand properly if it is followed by /.. . To see it at
>> your place please do the following.
>> cd /tmp
>> mkdir dir1
>> mkdir dir2
>> touch dir1/1.c
>> cd dir2
>> ln -s ../dir1 symlink
>> 
>> if we do ls symlink it gives 1.c as expected.
>> But if we do ls symlink/.. then it list contents of present directory.
>> 
>> @/tmp/dir2
>> $ ls symlink
>> 1.c
>> 
>> @/tmp/dir2
>> $ ls symlink/..
>> symlink
>> 
>> I think it should list contents of /tmp directory.
>> Could somebody throw some light over it.
>> 
>> regards
>> Vinay
>----- End forwarded message -----
>
>Looks like he has his point.  Under Linux it works as he describes it.
>In Cygwin the following happens. 
>
>normalize_posix_path simplifies the path first and strippes ".." by
>removing the previous entry in the path.  Then path_conv::check checks
>for symlinks and directories.  So, the incoming path /tmp/dir2/symlink/..
>becomes /tmp/dir2 after the call to normalize_posix_path and the symlink
>expansion in path_conv::check doesn't even see a symlink. 
>
>That reflects the typical behaviour in tcsh with the setting
>`set symlinks expand', but it doesn't allow any other behaviour.
>
>It looks like a fix would require to change the order in path_conv::check.
>The symlink expansion would have to be done before the path gets normalized.
>Or the symlink expansion could be moved into normalize_posix_path.

I thought about this and I think it would be tricky to get this right.
You have to do path normalization before you check the mount table to
even figure out where something like /foo/../symlink really lives.
symlink could also be a mount point.

cgf