Test OS predicates at runtime only

      ((eq :and (car x)) (every #'featurep (cdr x)))

      (t (error "Malformed feature specification ~S" x))))

  (defun os-unix-p ()

    "Is the underlying operating system some Unix variant?"

    (or #+abcl (featurep :unix)

        #+(and (not abcl) (or unix cygwin darwin)) t))

  ;; Starting with UIOP 3.1.5, these are runtime tests.

  ;; You may bind *features* with a copy of what your target system offers to test its properties.

  (defun os-macosx-p ()

    "Is the underlying operating system MacOS X?"

    ;; OS-MACOSX is not mutually exclusive with OS-UNIX,

    ;; in fact the former implies the latter.

    (or

     #+allegro (featurep :macosx)

     #+clisp (featurep :macos)

     (featurep :darwin)))

    (featurep '(:or :darwin (:and :allegro :macosx) (:and :clisp :macos))))

  (defun os-unix-p ()

    "Is the underlying operating system some Unix variant?"

    (or (featurep '(:or :unix :cygwin)) (os-macosx-p)))

  (defun os-windows-p ()

    "Is the underlying operating system Microsoft Windows?"

    (or #+abcl (featurep :windows)

        #+(and (not (or abcl unix cygwin darwin)) (or win32 windows mswindows mingw32 mingw64)) t))

    (and (not (os-unix-p)) (featurep '(:or :win32 :windows :mswindows :mingw32 :mingw64))))

  (defun os-genera-p ()

    "Is the underlying operating system Genera (running on a Symbolics Lisp Machine)?"

    (or #+genera t))

    (featurep :genera))

  (defun os-oldmac-p ()

    "Is the underlying operating system an (emulated?) MacOS 9 or earlier?"

    (or #+mcl t))

    (featurep :mcl))

  (defun detect-os ()

    "Detects the current operating system. Only needs be run at compile-time,