lispval-storage-type

Arguments: object &optional type

Returns information about storage classifications or of the storage-classification of an object.

If type is not given, then the object's storage attributes are examined, and the most specific description of these attributes is returned in the form of a keyword. The possible keywords are:

1. :immediate, which means the object is not referenced with a pointer (fixnums, e.g.)
2. :static, which means the object is stored in an area which is not garbage collected.
3. :tenured, which means the object is stored in oldspace (also called tenured space).
4. :new, which means the object is stored in newspace but will, if it survives, eventually be tenured.
5. :panified, which means that the object is stored in newspace and will never be tenured. (The name comes from Peter Pan, who never grew old.) See the note just below.
6. :weak, which means the object is in newspace, will not be tenured, and is a weak vector.
7. :finalized, which means that the object is a finalization.
8. :weak-key-non-panified, which means that the object is a weak-key vector in newspace, but may be tenured (after which it will no longer be weak).
9. :weak-key-panified, which means that the object is a weak-key vector in newspace which will not be tenured.
10. :stack-allocated, which means the object resides on a stack somewhere. Note that on a non-os-threads Lisp the value may be seen as :stack-allocated even if it is outside of the stack it resides and should have been called :static. An object for which lispval-storage-type returns :stack-allocated will still cause sys:pointer-storage-type to return :static when passed as an argument to it.

Note on :panified objects: Only system-created objects can have storage type :panified but sometimes these objects are created as a consequnce of user action. The key vector of a weak-keys hashtable is typically a :panified object, though this can be controlled. See cl:make-hash-table in implementation.htm.

type can be :all or one of the storage types keywords in the list above.

If type is :all, a list of possible storage types is returned (and the object argument is ignored). Thus, when type is :all, the call is for information about the current implementation of lispval-storage-type, which may be modified in a patch subsequent to the release.

If type is a storage type, lispval-storage-type returns true or nil as the storage type of object matches or does not match type. Here match means `is of that storage type', not `is eq to the value returned by lispval-storage-type when type is not specified'. If lispval-storage-type returns :weak when type is not specified, it will return true when type is :weak and when type is :new.

See gc.htm for a discussion of where Lisp objects are stored. lispval-storage-type replaces the now deprecated pointer-storage-type.

Example

;; A 1-d static array has storage type :STATIC
;; (2-d and higher dimension
;; static arrays have headers that are Lisp objects so they will have
;; storage type :NEW or :TENURED, but their data vectors
;; (available via INSPECT) 
;; will have storage type :STATIC):
CL-USER(24): (sys:lispval-storage-type 
               (make-array 3 :allocation :static
                           :element-type 'fixnum :initial-element 2))
:STATIC
;; Fixnums are immediates:
CL-USER(25): (sys:lispval-storage-type 22)
:IMMEDIATE
;; Most Lisp objects start in new space:
CL-USER(26): (setq a (cons 1 2))
(1 . 2)
CL-USER(27): (sys:lispval-storage-type a)
:NEW
;; And after surviving several scavenges, they typically
;; move to oldspace:
CL-USER(28): (gc) (gc) (gc) (gc) (gc)
CL-USER(29): (sys:lispval-storage-type a)
:TENURED

;;  Here we show the use of the TYPE argument:
CL-USER(30): (setq a (make-array 10 :weak t))
#(NIL NIL NIL NIL NIL NIL NIL NIL NIL NIL)
CL-USER(31): (sys:lispval-storage-type a)
:WEAK
CL-USER(32): (sys:lispval-storage-type a :new)
T
CL-USER(5): (sys:lispval-storage-type a :weak)
T
CL-USER(6): 

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This page was not revised from the 9.0 page.
Created 2015.5.21.