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Date: Mon, 31 Mar 2025 09:32:14 -0700
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Subject: Re: symbolic link curiousity in 3.6.0
To: =?UTF-8?Q?P=C3=A1draig_Brady?= <P@draigBrady.com>,
        Bruno Haible <bruno@clisp.org>, bug-gnulib@gnu.org, cygwin@cygwin.com,
        Coreutils <coreutils@gnu.org>
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On 2025-03-30 07:26, Pádraig Brady wrote:
> On 30/03/2025 13:50, Corinna Vinschen wrote:
>> In terms of coreutils, I think either ls(1) gobble_file() or
>> file_has_aclinfo_cache() should still handle ENOENT from
>> file_has_aclinfo() and not print any error message.  After all, due to
>> the preconditions for building acl_get_link_np, we can't be sure
>> acl_get_link_np has really been built into file-has-acl.c, and the
>> problem persists.
> 
> I tend to agree. I'll apply this later:
> 
> 
> commit 88385a0d6d56197d3c180432c8a4bca07241e90b (HEAD -> master)
> Author: Pádraig Brady <P@draigBrady.com>
> Date:   Sun Mar 30 15:16:54 2025 +0100
> 
>      ls: suppress ENOENT errors when reading ACL info
> 
>      * src/ls.c (gobble_file): Indicating unknown ACL info with '?'
>      suffices for the edge case of a file being removed while reading,
>      or older cygwin when reading through dangling symlinks.
>      Reported by Corinna Vinschen.

Not sure this is a good idea, as a file being removed while getting its 
attributes indicates a serious issue that's worth bringing to the user's 
attention more directly.

How about if we instead use O_PATH on the file first, and then use fstat 
etc. on the result? That should fix the 
file-removed-while-getting-attributes situation, at least on platforms 
with /proc/self/fd (which I assume includes Cygnus). I realize that 
flistxattr etc. don't work on fds opened via O_PATH (why? this seems 
silly, but it's not my bailiwick) but /proc/self/fd works around that 
problem.

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