[[
#if __FreeBSD__ == 4
error "No, in FreeBSD 4.0 recursive mutexes actually don't work."
+#elif (defined __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ \
+ && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 1070)
+error "No, in Mac OS X < 10.7 recursive mutexes actually don't work."
#else
int x = (int)PTHREAD_MUTEX_RECURSIVE;
return !x;