Make it possible to remove a closed IO::Socket handle from IO::Select.

Fixes #17447

MANIFEST

@@ -3670,6 +3670,7 @@ dist/IO/README			IO extension maintenance notice
 dist/IO/t/cachepropagate-tcp.t	See if IO::Socket duplication works
 dist/IO/t/cachepropagate-udp.t	See if IO::Socket duplication works
 dist/IO/t/cachepropagate-unix.t	See if IO::Socket duplication works
+dist/IO/t/gh17447.t		Tests fix for #17447
 dist/IO/t/IO.t			See if IO works
 dist/IO/t/io_const.t		See if constants from IO work
 dist/IO/t/io_dir.t		See if directory-related methods from IO work

META.json

@@ -81,6 +81,7 @@
          "dist/IO/t/cachepropagate-tcp.t",
          "dist/IO/t/cachepropagate-udp.t",
          "dist/IO/t/cachepropagate-unix.t",
+         "dist/IO/t/gh17447.t",
          "dist/IO/t/IO.t",
          "dist/IO/t/io_const.t",
          "dist/IO/t/io_dir.t",

META.yml

@@ -78,6 +78,7 @@ no_index:
     - dist/IO/t/cachepropagate-tcp.t
     - dist/IO/t/cachepropagate-udp.t
     - dist/IO/t/cachepropagate-unix.t
+    - dist/IO/t/gh17447.t
     - dist/IO/t/IO.t
     - dist/IO/t/io_const.t
     - dist/IO/t/io_dir.t

dist/IO/lib/IO/Select.pm

@@ -10,7 +10,7 @@ use     strict;
 use warnings::register;
 require Exporter;
 
-our $VERSION = "1.41";
+our $VERSION = "1.42";
 
 our @ISA = qw(Exporter); # This is only so we can do version checking
 
@@ -57,7 +57,21 @@ sub _fileno
  my($self, $f) = @_;
  return unless defined $f;
  $f = $f->[0] if ref($f) eq 'ARRAY';
- ($f =~ /^\d+$/) ? $f : fileno($f);
+ if($f =~ /^[0-9]+$/) { # plain file number
+  return $f;
+ }
+ elsif(defined(my $fd = fileno($f))) {
+  return $fd;
+ }
+ else {
+  # Neither a plain file number nor an opened filehandle; but maybe it was
+  # previously registered and has since been closed. ->remove still wants to
+  # know what fileno it had
+  foreach my $i ( FIRST_FD .. $#$self ) {
+   return $i - FIRST_FD if $self->[$i] == $f;
+  }
+  return undef;
+ }
 }
 
 sub _update

dist/IO/t/gh17447.t

@@ -0,0 +1,29 @@
+#!/usr/bin/perl
+
+# Regression test for https://github.com/Perl/perl5/issues/17447
+
+use strict;
+use warnings;
+
+use Test::More tests => 2;
+
+use IO::Select;
+use IO::Handle;
+
+pipe( my $rd, my $wr ) or die "Cannot pipe() - $!";
+binmode $rd;
+binmode $wr;
+$wr->syswrite("data\n");
+
+my $select = IO::Select->new();
+$select->add($rd);
+
+is( scalar $select->handles, 1, '$select has 1 handle' );
+
+# close first, then remove afterwards
+$rd->close;
+$select->remove($rd);
+
+is( scalar $select->handles, 0, '$select has 0 handles' );
+
+exit;