standard-instance-access (instance location)

The instance argument is an object.
The location argument is a slot location.

The result of this function is an object.

This function is called to provide direct access to a slot in an instance. By usurping the normal slot lookup protocol, this function is intended to provide highly optimized access to the slots associated with an instance. The following restrictions apply to the use of this function:

• The instance argument must be a standard instance (it must have been returned by allocate-instance (standard-class)).
• The instance argument cannot be an non-updated obsolete instance.
• The location argument must be a location of one of the directly accessible slots of the instance's class.
• The slot must be bound.

The results are undefined if any of these restrictions are not met.