// we wanted to.
		// We can't expand the GC program without extra storage
		// space we can't easily get.
		// Fortunately we have the type information.
		systemstack(func() {
			cgoCheckUsingType(typ, src, off, size)
		})
		return
	}

	// src must be in the regular heap.
	tp := s.typePointersOf(uintptr(src), size)
	for {
		var addr uintptr