Re: [RFC v1] man/man2/close.2: CAVEATS: Document divergence from POSIX.1-2024

* Vincent Lefevre:

On 2025-05-16 09:05:47 -0400, Rich Felker wrote:

quoted

FWIW musl adopted the EINPROGRESS as soon as we were made aware of the
issue, and later changed it to returning 0 since applications
(particularly, any written prior to this interpretation) are prone to
interpret EINPROGRESS as an error condition rather than success and
possibly misinterpret it as meaning the fd is still open and valid to
pass to close again.

If I understand correctly, this is a poor choice. POSIX.1-2024 says:

ERRORS
  The close() and posix_close() functions shall fail if:
[...]
  [EINPROGRESS]
    The function was interrupted by a signal and fildes was closed
    but the close operation is continuing asynchronously.

But this does not mean that the asynchronous close operation will
succeed.

So the application could incorrectly deduce that the close operation
was done without any error.

But on Linux, close traditionally has poor error reporting anyway.  You
have to fsync (or equivalent) before calling close if you want error
checking.  On other systems, the fsync is more or less implied by the
close, leading to rather poor performance.

Thanks,
Florian