llvm dev - Aug 2015 - Supporting symbolic links in Path library routines

include/llvm/Support/FileSystem.h has file_type which enumerates the file
system’s view of the file type.  One of the values is “symlink_file”.

But because the Unix implementation of status() calls stat() instead of lstat(),
if the path refers to a symbolic link, the link is followed.  There’s no way to
get information about the symbolic link itself.

I think changing status() to call lstat() is a bad idea, so it seems like the
only other option is to create a new routine when you explicitly want to check
if what the path refers to is a symbolic link.

Or this is such an uncommon case, that it’s the caller’s responsibility to
detect if a file path refers to a symbolic link in whatever platform appropriate
mechanism they have available to them.  If that’s the case, then I suggest
removing symlink_file from file_type.

Any comments?

Cameron Esfahani
dirty at apple.com

"There are times in the life of a nation when the only place a decent man
can find himself is in prison."

On Mon, Aug 17, 2015 at 6:32 PM, Cameron Esfahani via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> include/llvm/Support/FileSystem.h has file_type which enumerates the file
system’s view of the file type.  One of the values is “symlink_file”.
>
> But because the Unix implementation of status() calls stat() instead of
lstat(), if the path refers to a symbolic link, the link is followed.  There’s
no way to get information about the symbolic link itself.
>
> I think changing status() to call lstat() is a bad idea, so it seems like
the only other option is to create a new routine when you explicitly want to
check if what the path refers to is a symbolic link.
>
> Or this is such an uncommon case, that it’s the caller’s responsibility to
detect if a file path refers to a symbolic link in whatever platform appropriate
mechanism they have available to them.  If that’s the case, then I suggest
removing symlink_file from file_type.
>
> Any comments?
>
> Cameron Esfahani
> dirty at apple.com
>
> "There are times in the life of a nation when the only place a decent
man can find himself is in prison."
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org         http://llvm.cs.uiuc.edu
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
The API was designed as a mirror of the Boost Filesystem API. I'm not
surprised to see an unused enum member there. I don't believe any LLVM
tools care about symlinks, so I'm fine with removing it as long as no
platform will return that value.

- Michael Spencer

I’ll search through the code and proffer a patch if no one uses it.

Cameron Esfahani
dirty at apple.com

"Americans are very skilled at creating a custom meaning from something
that's mass-produced."

Ann Powers

> On Aug 19, 2015, at 6:48 PM, Michael Spencer <bigcheesegs at
gmail.com> wrote:
> 
> The API was designed as a mirror of the Boost Filesystem API. I'm not
> surprised to see an unused enum member there. I don't believe any LLVM
> tools care about symlinks, so I'm fine with removing it as long as no
> platform will return that value.
>

Looks like there is effectively dead code in clang that compares with
file_type::symlink_file. We can very likely nuke it too.

Thanks for finding this dead code.

Cheers,
Rafael


On 17 August 2015 at 21:32, Cameron Esfahani via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> include/llvm/Support/FileSystem.h has file_type which enumerates the file
system’s view of the file type.  One of the values is “symlink_file”.
>
> But because the Unix implementation of status() calls stat() instead of
lstat(), if the path refers to a symbolic link, the link is followed.  There’s
no way to get information about the symbolic link itself.
>
> I think changing status() to call lstat() is a bad idea, so it seems like
the only other option is to create a new routine when you explicitly want to
check if what the path refers to is a symbolic link.
>
> Or this is such an uncommon case, that it’s the caller’s responsibility to
detect if a file path refers to a symbolic link in whatever platform appropriate
mechanism they have available to them.  If that’s the case, then I suggest
removing symlink_file from file_type.
>
> Any comments?
>
> Cameron Esfahani
> dirty at apple.com
>
> "There are times in the life of a nation when the only place a decent
man can find himself is in prison."
>
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org         http://llvm.cs.uiuc.edu
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev