Function

Summary

Sets the weakness state of an array.

Package

hcl

Signature

set-array-weak array weakp => weakp

Arguments

array

A non-displaced array, with array-element-type t.

weakp

If weakp is non-nil, the array is made weak. If weakp is nil, the array is made non-weak.

Values

Returns weakp.

Description

By default, arrays are non-weak, and they keep alive all the objects that are stored in them. A weak array may remove a pointer if the object that it points to is not pointed to from somewhere else. When a pointer is removed like this, it is replaced in array with nil.

Pointers are replaced by nil after a garbage collector (GC) operation that identifies that they can be replaced. This means that if the object that is pointed to has been promoted to a higher generation, a garbage collection of the higher generation is required to remove the pointer. Note that by default the system does not automatically GC the blocking generation or higher.

The weakness state of an array can be changed many times.

In all implementations, array must not be a displaced array, and the array-element-type of array must be t.

In 64-bit LispWorks, an additional requirement is that array must be an adjustable array.

set-array-weak can be called at any moment.

Notes

An array can be made weak at creation time using the :weak argument to make-array.

See also

array-weak-p
copy-to-weak-simple-vector
set-hash-table-weak
make-array
mark-and-sweep
Freeing of objects by the GC