Q:

Garbage collector in Common lisp?

Is SBCL or CMUCL garbage collector available in Lisp implementation?

A:

SBCL exposes some of its GC functionality: http://john.freml.in/sbcl-optimise-gc

A:

Both of them provide garbage collection.
See this for CMUCL and this for SBCL.
Quote from Wikipedia:

Garbage collection was invented by
  John McCarthy around 1959 to solve
  problems in Lisp.

Every Common Lisp implementation, must have garbage collection defined, since any standard implementation must comply to Common Lisp ANSI standard.

A:

Both of them have GC available.
Like with any conformant Common Lisp implementation, you can do (gc :full t) to instruct garbage collector to collect all your unreachable objects.

