From @ribasushi

Consider this (procfs-specific) example​:

rabbit@​Ahasver​:~$ perl -e '
  close STDIN;
  close STDOUT;
  exec( $^X => -e => q(
  require Tie​::Hash;
  exec( $^X => -e => q(
  warn `ls -l /proc/$$/fd`
  ) )
  ) )
'
total 0
lr-x------ 1 rabbit rabbit 64 Jun 16 17​:57 0 -> /dev/null
lr-x------ 1 rabbit rabbit 64 Jun 16 17​:57 1 ->
/home/rabbit/perl5/perlbrew/perls/5.20.0/lib/5.20.0/Tie/Hash.pm
lrwx------ 1 rabbit rabbit 64 Jun 16 17​:57 2 -> /dev/pts/19
lr-x------ 1 rabbit rabbit 64 Jun 16 17​:57 3 -> pipe​:[2138010]

I would have expected that FD1 is closed after require() finishes. Yet
not only it stays open, but it is also inherited across exec().

Likely somewhere in the guts there is an over-eager check for "do not
touch anything with fileno <= 2", which ideally should be relaxed.

From @Leont

On Tue, Jun 16, 2015 at 5​:59 PM, Peter Rabbitson <perlbug-followup@​perl.org>
wrote​:

Consider this (procfs-specific) example​:

rabbit@​Ahasver​:~$ perl -e '
close STDIN;
close STDOUT;
exec( $^X => -e => q(
require Tie​::Hash;
exec( $^X => -e => q(
warn `ls -l /proc/$$/fd`
) )
) )
'
total 0
lr-x------ 1 rabbit rabbit 64 Jun 16 17​:57 0 -> /dev/null
lr-x------ 1 rabbit rabbit 64 Jun 16 17​:57 1 ->
/home/rabbit/perl5/perlbrew/perls/5.20.0/lib/5.20.0/Tie/Hash.pm
lrwx------ 1 rabbit rabbit 64 Jun 16 17​:57 2 -> /dev/pts/19
lr-x------ 1 rabbit rabbit 64 Jun 16 17​:57 3 -> pipe​:[2138010]

I would have expected that FD1 is closed after require() finishes. Yet

not only it stays open, but it is also inherited across exec().

Likely somewhere in the guts there is an over-eager check for "do not
touch anything with fileno <= 2", which ideally should be relaxed.

What's happening is something completely different, it's essentially a
refcounting issue. At startup, PerlIO does an fdopen to fd=0,1,2, assuming
they are open already(refcount=1). Then in runtime those descriptors are
opened for real (refcount=2) and then closed (refcount=1 again). The
inheriting across exec is $^F doing exactly what it's supposed to do.

I'm not sure what the solution is in this situation, TBH.

Leon

The RT System itself - Status changed from 'new' to 'open'