--- old/src/share/vm/utilities/copy.cpp	2016-02-09 19:35:00.129912656 -0800
+++ new/src/share/vm/utilities/copy.cpp	2016-02-09 19:35:00.021910741 -0800
@@ -64,6 +64,13 @@
    * @param elem_size size of the elements to copy-swap
    */
   static void conjoint_swap(address src, address dst, size_t byte_count, size_t elem_size) {
+    assert(src != NULL, "address must not be NULL");
+    assert(dst != NULL, "address must not be NULL");
+    assert(elem_size == 2 || elem_size == 4 || elem_size == 8,
+           "incorrect element size: " SIZE_FORMAT, elem_size);
+    assert(is_size_aligned(byte_count, elem_size),
+           "byte_count " SIZE_FORMAT " must be multiple of element size " SIZE_FORMAT, byte_count, elem_size);
+
     address src_end = src + byte_count;
 
     if (dst <= src || dst >= src_end) {