anchor.diff:    };
   
     inherit libsigsegv gettext coreutils;
  -  
  +
  +  ffcallAvailable = stdenv.isLinux && (libffcall != null);
  +
     buildInputs = [libsigsegv]
     ++ stdenv.lib.optional (gettext != null) gettext
     ++ stdenv.lib.optional (ncurses != null) ncurses
     ++ stdenv.lib.optional (pcre != null) pcre
     ++ stdenv.lib.optional (zlib != null) zlib
     ++ stdenv.lib.optional (readline != null) readline
  -  ++ stdenv.lib.optional (libffi != null) libffi
  -  ++ stdenv.lib.optional (libffcall != null) libffcall
  +  ++ stdenv.lib.optional (ffcallAvailable && (libffi != null)) libffi
  +  ++ stdenv.lib.optional ffcallAvailable libffcall
     ++ stdenv.lib.optionals x11Support [
       libX11 libXau libXt libXpm xproto libXext xextproto
     ];
  
positive.code:   configureFlags = "builddir"
    + stdenv.lib.optionalString (!dllSupport) " --without-dynamic-modules"
    + stdenv.lib.optionalString (readline != null) " --with-readline"
    + stdenv.lib.optionalString (libffi != null) " --with-dynamic-ffi"
    + stdenv.lib.optionalString (libffcall != null) " --with-ffcall"
    + stdenv.lib.concatMapStrings (x: " --with-module=" + x) withModules
    + stdenv.lib.optionalString threadSupport " --with-threads=POSIX_THREADS";
  
  
negative.code:     description = "ANSI Common Lisp Implementation";
      homepage = http://clisp.cons.org;
      maintainers = with stdenv.lib.maintainers; [raskin tohl];
      platforms = stdenv.lib.platforms.unix;
    };
  }
  