__getBlkInfo

Get the cached block info of an interior pointer. Returns null if the interior pointer's block is not cached.

NOTE: The following note was not valid, but is retained for historical purposes. The data cannot be cleared because the stack contains a reference to the affected block (e.g. through interior). Therefore, the element will not be collected, and the data will remain valid.

ORIGINAL: The base ptr in this struct can be cleared asynchronously by the GC, so any use of the returned BlkInfo should copy it and then check the base ptr of the copy before actually using it.