.. efun:: void set_this_object(object object_to_pretend_to_be)

  This is a privileged function, only to be used in the master object or in the simul_efun object.

  It changes the result of :efun:`this_object` in the using function, and the result of :efun:`previous_object` in functions called in other objects by :efun:`call_other`/:efun:`apply`/:efun:`funcall`. Its effect will remain till there is a return of an external function call, or another call of :efun:`set_this_object`. While executing code in the master object's program or the primary simul_efun object's program, :efun:`set_this_object` is granted even if :efun:`this_object` is altered by :efun:`set_this_object`. This does not apply to functions inherited from other programs.

  Use it with extreme care to avoid inconsistencies. After a call of :efun:`set_this_object`, some LPC-constructs might behave in an odd manner, or even crash the system. In particular, using global variables or calling local functions (except by call_other) is illegal and actively prevented.

  Allowed are :efun:`call_other`, map functions, access of local variables (which might hold array pointers to a global array), simple arithmetic and the assignment operators.

  .. limit:: It is currently not possible to directly restore the original current object. So instead of writing::

      object me = this_object();
      set_this_object(that);
      <some code>
      set_this_object(me);
      <more code>

    one has to use a workaround:::

      private void doit (object that) {
        set_this_object(that);
        <some code>
      }

      funcall(#'doit, that);
      <more code>

    Some people would consider this a feature.

  :history 3.2.10 changed: actively prevents references to global variables and function calls by address while :efun:`set_this_object` is in effect.

  .. seealso:: :efun:`this_object`, :efun:`set_this_player`