Hi,

I'm updating the manual pages for POSIX.1-2024, and have some doubts
about close(2).  The manual page for close(2) says (conforming to
POSIX.1-2008):

       The EINTR error is a somewhat special case.  Regarding the EINTR
       error, POSIX.1‐2008 says:

              If close() is interrupted by  a  signal  that  is  to  be
              caught,  it  shall  return -1 with errno set to EINTR and
              the state of fildes is unspecified.

       This permits the behavior that occurs on Linux  and  many  other
       implementations,  where,  as  with  other errors that may be re‐
       ported by close(), the  file  descriptor  is  guaranteed  to  be
       closed.   However, it also permits another possibility: that the
       implementation returns an EINTR error and  keeps  the  file  de‐
       scriptor open.  (According to its documentation, HP‐UX’s close()
       does this.)  The caller must then once more use close() to close
       the  file  descriptor, to avoid file descriptor leaks.  This di‐
       vergence in implementation behaviors provides a difficult hurdle
       for  portable  applications,  since  on  many   implementations,
       close() must not be called again after an EINTR error, and on at
       least one, close() must be called again.  There are plans to ad‐
       dress  this  conundrum for the next major release of the POSIX.1
       standard.

TL;DR: close(2) with EINTR is allowed to either leave the fd open or
closed, and Linux leaves it closed, while others (HP-UX only?) leaves it
open.

Now, POSIX.1-2024 says:

	If close() is interrupted by a signal that is to be caught, then
	it is unspecified whether it returns -1 with errno set to
	[EINTR] and fildes remaining open, or returns -1 with errno set
	to [EINPROGRESS] and fildes being closed, or returns 0 to
	indicate successful completion; [...]

<https://pubs.opengroup.org/onlinepubs/9799919799/functions/close.html>

Which seems to bless HP-UX and screw all the others, requiring them to
report EINPROGRESS.

Was there any discussion about what to do in the Linux kernel?


Have a lovely night!
Alex

-- 
<https://www.alejandro-colomar.es/>