anchor.diff:  ** slows down allocation
   ** limits available memory
   
  +-> achieved by moving all objects in contiguous blocks
  +
  +* can be quite slow
  +* needs to "stop the world"
  +
   
   GC Principles: "Generational Hypothesis"
   ----------------------------------------
  
positive.code: -----
  
  
  GC Principles: References Count
  -------------------------------
  
  But:
  
  
negative.code: without going through another object",
  i.e. all objects that _cannot_ be released.
  
  Or: GC roots are _external_ pointers, i.e. those where the parent and child
  are in different memory pools.
  
  * Class loaded by _system_ class loaders (not by custom ones)
  * Active threads
  * Local variables
  