Method: (FIND-BLOCK T FREE-LIST-HEAP)

Source

(defmethod find-block (min-size (heap free-list-heap))
  ;; Tries to find a block of a size that's at least the specified
  ;; minimum size.  If there is such a block, the block and the
  ;; block's size are returned.  Otherwise it returns nil.
  (let ((size-class (size-class min-size heap)))
    (loop for size-class from size-class below (nr-free-lists heap)
          do (let ((block (allocate-block heap :size min-size :expand nil)))
               (when block
                 (return (values block
                                 (size-class-block-size size-class heap))))))))