Reclaim storage for Lisp objects no longer needed.
Garbage collection happens automatically if you cons more than
`gc-cons-threshold' bytes of Lisp data since previous garbage collection.
`garbage-collect' normally returns a list with info on amount of space in use,
where each entry has the form (NAME SIZE USED FREE), where:
- NAME is a symbol describing the kind of objects this entry represents,
- SIZE is the number of bytes used by each one,
- USED is the number of those objects that were found live in the heap,
- FREE is the number of those objects that are not live but that Emacs
keeps around for future allocations (maybe because it does not know how
to return them to the OS).
However, if there was overflow in pure space, `garbage-collect'
returns nil, because real GC can't be done.
See Info node `(elisp)Garbage Collection'. (fn)