+#if defined(LISP_FEATURE_SB_THREAD)
+#define thread_self() pthread_self()
+#define thread_kill pthread_kill
+#define thread_sigmask pthread_sigmask
+#define thread_mutex_lock(l) pthread_mutex_lock(l)
+#define thread_mutex_unlock(l) pthread_mutex_unlock(l)
+#else
+#define thread_self() 0
+#define thread_kill kill_safely
+#define thread_sigmask sigprocmask
+#define thread_mutex_lock(l) 0
+#define thread_mutex_unlock(l) 0
+#endif
+
+/* #define QSHOW */ /* Enable low-level debugging output? */
+/* #define QSHOW_SAFE */ /* Enable blocking interrupts for each SHOW. */