+\f
+;;;; MAKE-LOAD-FORM stuff
+
+;;; The entry point for MAKE-LOAD-FORM support. When IR1 conversion
+;;; finds a constant structure, it invokes this to arrange for proper
+;;; dumping. If it turns out that the constant has already been
+;;; dumped, then we don't need to do anything.
+;;;
+;;; If the constant hasn't been dumped, then we check to see whether
+;;; we are in the process of creating it. We detect this by
+;;; maintaining the special *CONSTANTS-BEING-CREATED* as a list of all
+;;; the constants we are in the process of creating. Actually, each
+;;; entry is a list of the constant and any init forms that need to be
+;;; processed on behalf of that constant.
+;;;
+;;; It's not necessarily an error for this to happen. If we are
+;;; processing the init form for some object that showed up *after*
+;;; the original reference to this constant, then we just need to
+;;; defer the processing of that init form. To detect this, we
+;;; maintain *CONSTANTS-CREATED-SINCE-LAST-INIT* as a list of the
+;;; constants created since the last time we started processing an
+;;; init form. If the constant passed to emit-make-load-form shows up
+;;; in this list, then there is a circular chain through creation
+;;; forms, which is an error.
+;;;
+;;; If there is some intervening init form, then we blow out of
+;;; processing it by throwing to the tag PENDING-INIT. The value we
+;;; throw is the entry from *CONSTANTS-BEING-CREATED*. This is so the
+;;; offending init form can be tacked onto the init forms for the
+;;; circular object.
+;;;
+;;; If the constant doesn't show up in *CONSTANTS-BEING-CREATED*, then
+;;; we have to create it. We call MAKE-LOAD-FORM and check to see
+;;; whether the creation form is the magic value
+;;; :JUST-DUMP-IT-NORMALLY. If it is, then we don't do anything. The
+;;; dumper will eventually get its hands on the object and use the
+;;; normal structure dumping noise on it.
+;;;
+;;; Otherwise, we bind *CONSTANTS-BEING-CREATED* and
+;;; *CONSTANTS-CREATED-SINCE- LAST-INIT* and compile the creation form
+;;; much the way LOAD-TIME-VALUE does. When this finishes, we tell the
+;;; dumper to use that result instead whenever it sees this constant.
+;;;
+;;; Now we try to compile the init form. We bind
+;;; *CONSTANTS-CREATED-SINCE-LAST-INIT* to NIL and compile the init
+;;; form (and any init forms that were added because of circularity
+;;; detection). If this works, great. If not, we add the init forms to
+;;; the init forms for the object that caused the problems and let it
+;;; deal with it.
+(defvar *constants-being-created* nil)
+(defvar *constants-created-since-last-init* nil)
+;;; FIXME: Shouldn't these^ variables be bound in LET forms?
+(defun emit-make-load-form (constant)
+ (aver (fasl-output-p *compile-object*))
+ (unless (or (fasl-constant-already-dumped-p constant *compile-object*)
+ ;; KLUDGE: This special hack is because I was too lazy
+ ;; to rework DEF!STRUCT so that the MAKE-LOAD-FORM
+ ;; function of LAYOUT returns nontrivial forms when
+ ;; building the cross-compiler but :IGNORE-IT when
+ ;; cross-compiling or running under the target Lisp. --
+ ;; WHN 19990914
+ #+sb-xc-host (typep constant 'layout))
+ (let ((circular-ref (assoc constant *constants-being-created* :test #'eq)))
+ (when circular-ref
+ (when (find constant *constants-created-since-last-init* :test #'eq)
+ (throw constant t))
+ (throw 'pending-init circular-ref)))
+ (multiple-value-bind (creation-form init-form)
+ (handler-case
+ (sb!xc:make-load-form constant (make-null-lexenv))
+ (error (condition)
+ (compiler-error "(while making load form for ~S)~%~A"
+ constant
+ condition)))
+ (case creation-form
+ (:just-dump-it-normally
+ (fasl-validate-structure constant *compile-object*)
+ t)
+ (:ignore-it
+ nil)
+ (t
+ (compile-top-level-lambdas () t)
+ (when (fasl-constant-already-dumped-p constant *compile-object*)
+ (return-from emit-make-load-form nil))
+ (let* ((name (let ((*print-level* 1) (*print-length* 2))
+ (with-output-to-string (stream)
+ (write constant :stream stream))))
+ (info (if init-form
+ (list constant name init-form)
+ (list constant))))
+ (let ((*constants-being-created*
+ (cons info *constants-being-created*))
+ (*constants-created-since-last-init*
+ (cons constant *constants-created-since-last-init*)))
+ (when
+ (catch constant
+ (fasl-note-handle-for-constant
+ constant
+ (compile-load-time-value
+ creation-form
+ (format nil "creation form for ~A" name))
+ *compile-object*)
+ nil)
+ (compiler-error "circular references in creation form for ~S"
+ constant)))
+ (when (cdr info)
+ (let* ((*constants-created-since-last-init* nil)
+ (circular-ref
+ (catch 'pending-init
+ (loop for (name form) on (cdr info) by #'cddr
+ collect name into names
+ collect form into forms
+ finally
+ (compile-make-load-form-init-forms
+ forms
+ (format nil "init form~:[~;s~] for ~{~A~^, ~}"
+ (cdr forms) names)))
+ nil)))
+ (when circular-ref
+ (setf (cdr circular-ref)
+ (append (cdr circular-ref) (cdr info))))))))))))
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