问题
My program is getting errors with multithreading, so I want to expand the with-lock-grabbed macro to keep track of the stack of locks a process acquires. I want to do this by simply adding a slot to process to store the lock-stack.
Unfortunately, I don't understand how to add a slot at runtime without destroying what's already there. ensure-class completely redefines the class. I don't want this, since I don't know what other slots process already has.
How can I add a slot? In particular, I would like to add these two slots:
(lock-stack :documentation "stores a list of all locks of the process.
Only used for debugging"
:type list
:initform nil
:accessor lock-stack-acc
)
(lock-stack-error-found :documentation "indicates that an error on the locks was already found.
Only used for debugging"
:type boolean
:initform nil
:accessor lock-stack-error-found-acc
)
回答1:
Someone on GoogleGroups linked me to the answer: https://groups.google.com/group/comp.lang.lisp/msg/7e24e8417cd1b6e6?dmode=source
(defun direct-slot-defn->initarg (slot-defn)
(list :name (slot-definition-name slot-defn)
:readers (slot-definition-readers slot-defn)
:writers (slot-definition-writers slot-defn)
:initform (slot-definition-initform slot-defn)
:initargs (slot-definition-initargs slot-defn)
:initfunction (slot-definition-initfunction slot-defn)))
(defun add-slot-to-class (class name &key (initform nil)
accessors readers writers
initargs
(initfunction (constantly nil)))
(check-type class symbol)
(let ((new-slots (list (list :name name
:readers (union accessors readers)
:writers (union writers
(mapcar #'(lambda (x)
(list 'setf
x))
accessors)
:test #'equal)
:initform initform
:initargs initargs
:initfunction initfunction))))
(dolist (slot-defn (class-direct-slots (find-class class)))
(push (direct-slot-defn->initarg slot-defn)
new-slots))
(ensure-class class :direct-slots new-slots)))
来源：https://stackoverflow.com/questions/17002816/lisp-clos-adding-a-slot-to-the-process-class