On Windows, avoid hang when closing read end of pipe.

Fixes cpan-authors#77

lib/IPC/Run.pm

@@ -1273,6 +1273,24 @@ sub _empty($) { !( defined $_[0] && length $_[0] ) }
 sub _close {
     confess 'undef' unless defined $_[0];
     my $fd = $_[0] =~ /^\d+$/ ? $_[0] : fileno $_[0];
+    if (Win32_MODE) {
+
+        # Closing the read end of a pipe hangs if another process is in a read
+        # attempt on the read end's handle
+        # (https://github.com/Perl/perl5/issues/19963).  Work around that by
+        # first using dup2() to replace the FD with a non-pipe FD.
+        #
+        # Since start() and other user-facing method calls _close() many FDs, we
+        # could optimize this by opening and closing the non-pipe FD just once
+        # per method call.
+        my $nul_fd = POSIX::open 'NUL';
+        croak "$!: open( NUL )" unless defined $nul_fd;
+        my $r = POSIX::dup2( $nul_fd, $fd );
+        croak "$!: dup2( $nul_fd, $fd )" unless defined $r;
+        $r = POSIX::close $nul_fd;
+        _debug "close( $fd (NUL) ) = ERROR $!"
+          if _debugging_details && !defined $r;
+    }
     my $r = POSIX::close $fd;
     $r = $r ? '' : " ERROR $!";
     delete $fds{$fd};
@@ -2836,6 +2854,11 @@ sub start {
                         $kid->{OPS},
                     );
                     _debug "spawn() = ", $kid->{PID} if _debugging;
+                    if ($self->{_sleep_after_win32_spawn}) {
+                      sleep $self->{_sleep_after_win32_spawn};
+                      _debug "after sleep $self->{_sleep_after_win32_spawn}"
+                          if _debugging;
+                    }
                 }
             };
             if ($@) {

t/run.t

@@ -1028,6 +1028,9 @@ $fd_map = _map_fds;
 $h      = start(
     [ @perl, '-pe', 'BEGIN { $| = 1 } print STDERR uc($_)' ],
     \$in, \$out, \$err,
+
+    # hangs w/o fix for https://github.com/toddr/IPC-Run/issues/77
+    _sleep_after_win32_spawn => 1,
 );
 isa_ok( $h, 'IPC::Run' );
 is( $?, 99 );