"garbage collection"

[A Soare]

What is "garbage collection" from Feval is good for in this place?


DEFUN ("eval", Feval, Seval, 1, 1, 0,
       doc: /* Evaluate FORM and return its value.  */)
     (form)
     Lisp_Object form;
{
  Lisp_Object fun, val, original_fun, original_args;
  Lisp_Object funcar;
  struct backtrace backtrace;
  struct gcpro gcpro1, gcpro2, gcpro3;

  if (handling_signal)
    abort ();

  if (SYMBOLP (form))
    return Fsymbol_value (form);
  if (!CONSP (form))
    return form;

  QUIT;
  if ((consing_since_gc > gc_cons_threshold
       && consing_since_gc > gc_relative_threshold)
      ||
      (!NILP (Vmemory_full) && consing_since_gc > memory_full_cons_threshold))
    {
      GCPRO1 (form);
      Fgarbage_collect ();
      UNGCPRO;
    }

Merci d'avance.