-#else
-/* USE_THREADS is not defined */
-#define MUTEX_LOCK(m)
-#define MUTEX_LOCK_NOCONTEXT(m)
-#define MUTEX_UNLOCK(m)
-#define MUTEX_UNLOCK_NOCONTEXT(m)
-#define MUTEX_INIT(m)
-#define MUTEX_DESTROY(m)
-#define COND_INIT(c)
-#define COND_SIGNAL(c)
-#define COND_BROADCAST(c)
-#define COND_WAIT(c, m)
-#define COND_DESTROY(c)
-#define LOCK_SV_MUTEX
-#define UNLOCK_SV_MUTEX
-#define LOCK_STRTAB_MUTEX
-#define UNLOCK_STRTAB_MUTEX
-
-#define THR
-#define dTHR dNOOP
-#endif /* USE_THREADS */
+#ifndef COND_INIT
+# define COND_INIT(c)
+#endif
+
+#ifndef COND_SIGNAL
+# define COND_SIGNAL(c)
+#endif
+
+#ifndef COND_BROADCAST
+# define COND_BROADCAST(c)
+#endif
+
+#ifndef COND_WAIT
+# define COND_WAIT(c, m)
+#endif
+
+#ifndef COND_DESTROY
+# define COND_DESTROY(c)
+#endif
+
+#ifndef LOCK_DOLLARZERO_MUTEX
+# define LOCK_DOLLARZERO_MUTEX
+#endif
+
+#ifndef UNLOCK_DOLLARZERO_MUTEX
+# define UNLOCK_DOLLARZERO_MUTEX
+#endif
+
+/* THR, SET_THR, and dTHR are there for compatibility with old versions */
+#ifndef THR
+# define THR PERL_GET_THX
+#endif
+
+#ifndef SET_THR
+# define SET_THR(t) PERL_SET_THX(t)
+#endif
+
+#ifndef dTHR
+# define dTHR dNOOP
+#endif
+
+#ifndef INIT_THREADS
+# define INIT_THREADS NOOP
+#endif
+
+/*
+ * Local variables:
+ * c-indentation-style: bsd
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ *
+ * ex: set ts=8 sts=4 sw=4 et:
+ */