ObjFW  Diff

				    PTHREAD_MUTEX_RECURSIVE);
			], [
				AC_DEFINE(OF_HAVE_RECURSIVE_PTHREAD_MUTEXES, 1,
					[If pthread mutexes can be recursive])
			])

			AC_CHECK_FUNC(pthread_spin_lock, [
				have_spinlocks="yes"
				AC_DEFINE(OF_HAVE_PTHREAD_SPINLOCKS, 1,
					[Whether we have pthread spinlocks])
			])

			AC_CHECK_FUNC(sched_yield, [
				AC_DEFINE(OF_HAVE_SCHED_YIELD, 1,
					[Whether we have sched_yield()])

	printf "  ** To get optimal performance and be able to use all "
	echo "features, you should "
	echo "  ** install Clang >= 3.2."
	echo
])

AS_IF([test x"$enable_threads" != x"no" -a x"$atomic_ops" = x"none" \
    -a x"$have_spinlocks" != x"yes"], [
	echo
	printf "  ** Warning: You have enabled threads, but neither atomic "
	echo "operations nor"
	printf "  ** spinlocks are available. Expect *very* poor performance, "
	echo "as a mutex will"
	printf "  ** be locked for every retain and release! If you don't "
	echo "need threads, try"
	echo "  ** --disable-threads to work around this problem."
	echo
])