(cl:in-package #:sod)
+;;;--------------------------------------------------------------------------
+;;; Finalization error handling.
+
+;; These variables are internal to the implementation.
+(defvar-unbound *finalization-errors*
+ "A list of tokens for errors reported about the class being finalized.
+
+ During finalization, this is bound to a list of tokens corresponding to
+ the problems which have been reported so far via `finalization-error'.")
+(defvar-unbound *finalization-error-token*
+ "The token to store in `*finalization-errors*' in the event of an error.")
+
+(export 'finalization-error)
+(defmacro finalization-error ((token &rest args) &body body)
+ "Check for a kind of finalization error denoted by TOKEN and the ARGS.
+
+ The TOKEN and ARGS are convered into an error token as follows. If no
+ ARGS are given, then the TOKEN itself is evaluated and used directly;
+ otherwise, the token is a list whose first element is the result of
+ evaluating TOKEN, and the remaining elements are the results of evaluating
+ the ARGS. Error tokens are compared with `equal'.
+
+ If a finalization error denoted by this token has already been reported,
+ then do nothing: the BODY is not evaluated, and the result is nil.
+ Special exception: a nil token denotes a `generic' error which can be
+ repeated indefintely.
+
+ If the BODY signals an error (and doesn't handle it), then the error token
+ is added to a list of reported errors. That way, future calls to
+ `finalization-error' with an equal error token won't cause the user to be
+ inundated with duplicate reports."
+ `(let ((*finalization-error-token* ,(if (null args) token
+ `(list ,token ,@args))))
+ ,@body))
+
+(export 'finalization-failed)
+(defun finalization-failed ()
+ "Give up on finalizing the current class."
+ (throw '%finalization-failed nil))
+
;;;--------------------------------------------------------------------------
;;; Protocol definition.
If the chains are ill-formed (i.e., not distinct) then an error is
signalled."))
-(export 'guess-metaclass)
-(defgeneric guess-metaclass (class)
+(export 'check-class-initializer)
+(defgeneric check-class-initializer (slot class)
(:documentation
- "Determine a suitable metaclass for the CLASS.
+ "Check that SLOT has an appropriate initializer.
- The default behaviour is to choose the most specific metaclass of any of
- the direct superclasses of CLASS, or to signal an error if that failed."))
+ Signal an appropriate continuable error, possibly protected by
+ `finalization-error'.
+
+ The initializer might come either from the SLOT's defining class (which it
+ already knows), or from the prospective instance CLASS, of which the
+ defining class will be (a superclass of) the metaclass. Or, if the slot
+ is magical, then the initial value might come from somewhere else and it
+ might be forbidden for a programmer to set it explicitly."))
(export 'check-sod-class)
(defgeneric check-sod-class (class)
* The layout chains are computed.
+ Returns a generalized boolean: non-nil if the class has been successfully
+ finalized -- either just now, or if it was finalized already and nothing
+ needed to be done -- or nil if finalization failed -- either just now, or
+ because the class had previously been marked as broken following a failed
+ finalization attempt.
+
User methods can assume that the class in question has not yet been
- finalized. Errors during finalization can be reported in the usual
- way."))
+ finalized. Errors during finalization can be reported in the usual way.
+ See also `finalization-error' and `finalization-failed' above."))
;;;----- That's all, folks --------------------------------------------------
~mdw / sod / blobdiff