3 ;;; Class finalization protocol
5 ;;; (c) 2009 Straylight/Edgeware
8 ;;;----- Licensing notice ---------------------------------------------------
10 ;;; This file is part of the Sensible Object Design, an object system for C.
12 ;;; SOD is free software; you can redistribute it and/or modify
13 ;;; it under the terms of the GNU General Public License as published by
14 ;;; the Free Software Foundation; either version 2 of the License, or
15 ;;; (at your option) any later version.
17 ;;; SOD is distributed in the hope that it will be useful,
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19 ;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20 ;;; GNU General Public License for more details.
22 ;;; You should have received a copy of the GNU General Public License
23 ;;; along with SOD; if not, write to the Free Software Foundation,
24 ;;; Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
28 ;;;--------------------------------------------------------------------------
29 ;;; Finalization error handling.
31 ;; These variables are internal to the implementation.
32 (defvar-unbound *finalization-errors*
33 "A list of tokens for errors reported about the class being finalized.
35 During finalization, this is bound to a list of tokens corresponding to
36 the problems which have been reported so far via `finalization-error'.")
37 (defvar-unbound *finalization-error-token*
38 "The token to store in `*finalization-errors*' in the event of an error.")
40 (export 'finalization-error)
41 (defmacro finalization-error ((token &rest args) &body body)
42 "Check for a kind of finalization error denoted by TOKEN and the ARGS.
44 The TOKEN and ARGS are convered into an error token as follows. If no
45 ARGS are given, then the TOKEN itself is evaluated and used directly;
46 otherwise, the token is a list whose first element is the result of
47 evaluating TOKEN, and the remaining elements are the results of evaluating
48 the ARGS. Error tokens are compared with `equal'.
50 If a finalization error denoted by this token has already been reported,
51 then do nothing: the BODY is not evaluated, and the result is nil.
52 Special exception: a nil token denotes a `generic' error which can be
55 If the BODY signals an error (and doesn't handle it), then the error token
56 is added to a list of reported errors. That way, future calls to
57 `finalization-error' with an equal error token won't cause the user to be
58 inundated with duplicate reports."
59 `(let ((*finalization-error-token* ,(if (null args) token
60 `(list ,token ,@args))))
63 (export 'finalization-failed)
64 (defun finalization-failed ()
65 "Give up on finalizing the current class."
66 (throw '%finalization-failed nil))
68 ;;;--------------------------------------------------------------------------
69 ;;; Protocol definition.
72 (defgeneric compute-cpl (class)
74 "Returns the class precedence list for CLASS."))
76 (export 'compute-chains)
77 (defgeneric compute-chains (class)
79 "Compute the layout chains for CLASS.
81 Returns the following three values.
83 * the head of the class's primary chain;
85 * the class's primary chain as a list, most- to least-specific; and
87 * the complete collection of chains, as a list of lists, each most- to
88 least-specific, with the primary chain first.
90 These values will be stored in the CHAIN-HEAD, CHAIN and CHAINS slots.
92 If the chains are ill-formed (i.e., not distinct) then an error is
95 (export 'check-class-initializer)
96 (defgeneric check-class-initializer (slot class)
98 "Check that SLOT has an appropriate initializer.
100 Signal an appropriate continuable error, possibly protected by
101 `finalization-error'.
103 The initializer might come either from the SLOT's defining class (which it
104 already knows), or from the prospective instance CLASS, of which the
105 defining class will be (a superclass of) the metaclass. Or, if the slot
106 is magical, then the initial value might come from somewhere else and it
107 might be forbidden for a programmer to set it explicitly."))
109 (export 'check-sod-class)
110 (defgeneric check-sod-class (class)
112 "Check the CLASS for validity.
114 This is done as part of class finalization. The checks performed are as
117 * The class name and nickname, and the names of messages, obey the
118 rules (see VALID-NAME-P).
120 * The messages and slots have distinct names.
122 * The classes in the class-precedence-list have distinct nicknames.
124 * The chain-link is actually a proper (though not necessarily direct)
127 * The chosen metaclass is actually a subclass of all of the
128 superclasses' metaclasses.
130 If no attempt has previously been made to finalize the class, then errors
131 are signalled for the problems found. If finalizing it has been tried
132 before and failed (or this is a recursive attempt to finalize the class)
133 then nil is returned immediately. Otherwise a non-nil value is
136 (export 'finalize-sod-class)
137 (defgeneric finalize-sod-class (class)
139 "Computes all of the gory details about a class.
141 Once one has stopped inserting methods and slots and so on into a class,
142 one needs to finalize it to determine the layout structure and the class
143 precedence list and so on. More precisely that gets done is this:
145 * Related classes (i.e., direct superclasses and the metaclass) are
146 finalized if they haven't been already.
148 * If you've been naughty and failed to store a list of slots or
149 whatever, then an empty list is inserted.
151 * The class precedence list is computed and stored.
153 * The class is checked for compiance with the well-formedness rules.
155 * The layout chains are computed.
157 Returns a generalized boolean: non-nil if the class has been successfully
158 finalized -- either just now, or if it was finalized already and nothing
159 needed to be done -- or nil if finalization failed -- either just now, or
160 because the class had previously been marked as broken following a failed
161 finalization attempt.
163 User methods can assume that the class in question has not yet been
164 finalized. Errors during finalization can be reported in the usual way.
165 See also `finalization-error' and `finalization-failed' above."))
167 ;;;----- That's all, folks --------------------------------------------------