Ensure that all FH are closed and the subprocess is reaped upon System::Command object destruction.

lib/System/Command.pm

@@ -376,6 +376,49 @@ sub close {
     return $_[0];
 }
 
+sub DESTROY {
+
+    # ensure that all FH are closed. IO objects are special, and
+    # sometimes are not destroyed when references to them disappear.
+
+    # Here's some example code:
+
+    # {
+    #   my $cmd = System::Command->new( 'cat' );
+    #   $cmd->stdin->say( $_ ) for 0 ... 100;
+    # };
+
+    # When the block ends, $cmd will be destroyed.  Sometimes the
+    # order of destruction is
+
+    # System::Command, IO::Handle, System::Command::Reaper
+
+    # and sometimes it is
+
+    # System::Command, System::Command::Reaper
+
+    # experimentally, when the Reaper object is destroyed ( regardless
+    # of whether the IO::Handles are destroyed first) it never has
+    # access to its cached IO::Handle objects; when the Command object
+    # is destroyed, it releases its references to them, and because
+    # the Reaper object only has weak references to them, they
+    # disappear.
+
+    # So, if the IO::Handle destructor isn't called, the handles still
+    # exist, but Reaper doesn't close them, and if the subprocess is
+    # waiting on input, it will never exit, cannot be reaped,
+    # and Reaper::_reap will hang forever.
+
+    # note that explicitly closing the handles via $cmd->close
+    # is not safe, as, if the program is interrupted before the close,
+    # and the signal handler throws, e.g. $SIG{INT} = sub { die },
+    # the $cmd->close does not get fired.
+
+    # so, just make sure things are closed
+
+    $_[0]{reaper} and $_[0]->close;
+}
+
 1;
 
 __END__