<?php
//ob_start();
        $a=array();
        $a[]=&$a;
        array_pop($a);
        var_dump($GLOBALS);
//ob_end_flush();
?>
This piece of code causes infinite loop.
If the commments are removed than this little scripts starts to eat memory too fast. 100MB for 15secs. When the physical RAM was not available started to eat from the swap.
If var_export() is used no problems(with the CVS).
With 4.1.2 only causes Fatal Error - too deep recursion. Proably this has something with Yasuo's patch that tried force var_dump() to work like print_r() - showing recursion not just crashing.