+ ;; Kernel support for futexes (so-called "fast userspace mutexes") is
+ ;; available in Linux 2.6 and some versions of 2.4 (Red Hat vendor
+ ;; kernels, possibly other vendors too). We can take advantage of
+ ;; these to do faster and probably more reliable mutex and condition
+ ;; variable support. An SBCL built with this feature will fall back
+ ;; to the old system if the futex() syscall is not available at
+ ;; runtime
+ ; :sb-futex
+
+ ;; Support for detection of unportable code (when applied to the
+ ;; COMMON-LISP package, or SBCL-internal pacakges) or bad-neighbourly
+ ;; code (when applied to user-level packages), relating to material
+ ;; alteration to packages or to bindings in symbols in packages.
+ :sb-package-locks
+
+ ;; Support for the entirety of the 21-bit character space defined by
+ ;; the Unicode consortium, rather than the classical 8-bit ISO-8859-1
+ ;; character set.
+ :sb-unicode
+