Re: [boost] Filesystem: remove_all should not follow symlinks

From: Victor A. Wagner, Jr. (vawjr_at_[hidden])
Date: 2003-11-24 16:06:18

There _is_ a mechanism for creating hard links to directories on NTFS.  I 
don't know what the relevant runtime calls are, but I have a utility that 
creates them.  When you do a dir on a directory which has some they show up 
as <JUNCTION> instead of <DIR> see following:

  Directory of C:\Projects\Include

2003-11-24  02:02    <DIR>          .
2003-11-24  02:02    <DIR>          ..
2003-11-22  06:34                37 .cvsignore
2003-11-01  23:56    <JUNCTION>     boost
2003-04-27  11:13    <DIR>          Ced
2003-11-24  02:02    <DIR>          CVS
2003-04-27  11:13    <DIR>          Datx
2003-04-27  11:13    <DIR>          Edt
2003-04-27  11:13    <DIR>          FlexLM
2003-04-27  11:13    <DIR>          igloo
2003-04-27  11:13    <DIR>          Intel
2003-10-14  21:01    <DIR>          KokopelliTechnology
2003-04-27  11:13    <DIR>          Matlab
2003-04-27  11:13    <DIR>          Mcc
2003-08-19  13:09    <DIR>          Nlx
2003-11-22  07:39    <DIR>          PGL7.1
2003-11-01  23:57    <JUNCTION>     python
2003-11-03  10:55    <DIR>          QtPGL
2003-04-27  11:13    <DIR>          Rainbow
2003-04-27  11:13    <DIR>          Rsa
2003-04-27  11:13    <DIR>          Sealevel
2003-11-02  16:17    <JUNCTION>     sqlite
2003-04-27  11:13    <DIR>          Utility
                1 File(s)             37 bytes
               22 Dir(s)  16,553,005,056 bytes free
At Monday 2003-11-24 11:47, you wrote:
>Peter Dimov wrote:
>
> >Beman Dawes wrote:
> >> At 05:53 PM 11/21/2003, Peter Dimov wrote:
> >
> >[about reference counted links]
> >
> >>> It doesn't make sense to talk about shallow or deep semantics here.
> >>
> >> That's usually correct, but there are a few query operations where the
> >> shallow/deep issue might matter, depending on the operating system.
> >> Size/date/time being examples.
> >
> >Do you have a specific OS in mind? Size is a particularly interesting
> >example. ;-)
>
>No, except that size is problematic on many file systems, so it wouldn't 
>surprise me at all if size for a reference counted link is sometimes 
>troublesome.
>
>That being said, Boost.Filesystem could support a create_link() function 
>based on POSIX link() and Windows CreateHardLink(). While it would be 
>portable between POSIX and Windows for files, for directories it would 
>always fail on Windows, and might fail on POSIX (because the functionality 
>is optional for POSIX directories.
>
>I'm somewhat worried about providing a function with so many caveats. 
>Also, no one has asked for it.
>
> >From C++ point of view it is reasonable to consider a symlink something
> >that when passed to std::fopen actually opens another file. Under this
> >definition .lnk does not appear to be a symlink.
>
>Yes, that's what I've been thinking. So I don't think Boost.Filesystem 
>should provide a function to create symlinks; it would be too non-portable.
>
>OTOH, providing an is_symbolic_link() function which always returns false 
>on Windows would allow users to write correct portable directory recursion 
>programs similar to remove_all.
>
>--Beman
>
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Victor A. Wagner Jr.      http://rudbek.com
The five most dangerous words in the English language:
               "There oughta be a law"