// (and the fallback doesn't work...). Illumos does not.
	pthread_getattr_np(pthread_self(), &attr);  // GNU extension
	pthread_attr_getstack(&attr, &addr, &size); // low address
#elif defined(__illumos__)
	pthread_attr_get_np(pthread_self(), &attr);
	pthread_attr_getstack(&attr, &addr, &size); // low address
#else
	// We don't know how to get the current stacks, so assume they are the
	// same as the default stack bounds.