Working on dereferencing session variables.

Help/State.cl

@@ -177,10 +177,14 @@
 (defun do-close-problem ()
    ;; empty symbol table and entry list
    (empty-symbol-table)
+   (fill **grammar** nil) ;shallow dereference, for garbage collection
    (setf **grammar** nil)
-   (setq *StudentEntries* nil)
+   (fill *StudentEntries* nil) ;shallow dereference, for garbage collection
+   (setf *StudentEntries* nil)
 
    ;; unload current problem with its sgraph structures
+   ;; Garbage collection for problems may be complicated,
+   ;; since it may use stuff that is shared across problems
    (setf *cp* NIL)
 
    ;; Set the current problem instance time from the universal time.

Help/sessions.cl

@@ -148,7 +148,9 @@
 	)
 
 ;; New method with 
-(defstruct help-env "Quantities that must be saved between turns of a session.  Member vals contains list of values for help-env-vars." 
+;; Use type vector to make dereferencing easy.
+(defstruct help-env ; (help-env (:type vector)) 
+  "Quantities that must be saved between turns of a session.  Member vals contains list of values for help-env-vars." 
 	   section student problem vals)
 
 ;; Should be useful for debugging.
@@ -187,7 +189,7 @@
     `(progn
       ;; Null webserver:*env* indicates that the student is trying to work
       ;; on a session that has timed out or has not been initialized:  
-      (if (and webserver:*env* (help-env-p webserver:*env*))
+      (if (and webserver:*env* (help-env-p webserver:*env*)) ;(vectorp webserver:*env*))
 	  (let ,(mapcar 
 		 #'(lambda (x) (list x '(pop (help-env-vals webserver:*env*))))
 		 help-env-vars)
@@ -727,8 +729,33 @@
 		  (:URL . "http://www.webassign.net/something/or/other"))
 		result)
 	  result))
+    (fill (help-env-vals webserver:*env*) nil)
+;    (fill webserver:*env* nil)
+;    (dereference webserver:*env*)
+
     ;; Tell the session manager that the session is over.
     ;; Must be done after env-wrap
     (setf webserver:*env* nil)))
 
-;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+(defvar *dereferenced*) ;define symbol, but don't bind
+
+(defun dereference (x)
+  (cond 
+    ((or (stringp x) (symbolp x) (numberp x)))
+    ((consp x)
+     (dereference (car x)) (setf (car x) '*dereferenced*)
+     (dereference (cdr x)) (setf (cdr x) '*dereferenced*))
+    ((vectorp x)
+     (loop for y across x do (dereference y) (setf y '*dereferenced*)))
+    ;; Most structures are hard to think about, since
+    ;; data may be shared across problems and they are 
+    ;; hard to derefernce.
+    ((or (runtime-test-p x) (htime-p x) (turn-p x) (cmd-p x)
+	 (Enode-p x) (SystemEntry-p x) 
+	 (MT19937:random-state-p x) ;random number generator seed
+	 #+sbcl (sb-ext:process-p x))) ;solver process
+    (t
+     (format webserver:*stdout* "unknown type ~A for ~A~%" (type-of x) x))))
+
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

Help/symbols.cl

@@ -141,6 +141,7 @@
   (setf (cdr (get-variables-table x)) new-variables))
 
 (defun empty-symbol-table ()
+    (fill *variables* nil) ;shallow dereference, for garbage collection
     (setf *variables* (mapcar #'list *variable-namespaces*)))
 
 ;;-----------------------------------------------------------------------------