btr_cur_search_to_nth_level(): Add a debug assertion

and some Valgrind instrumentation.

storage/innobase/btr/btr0cur.c

@@ -321,7 +321,12 @@ btr_cur_search_to_nth_level(
 	ut_ad(dict_index_check_search_tuple(index, tuple));
 	ut_ad(!(index->type & DICT_IBUF) || ibuf_inside());
 	ut_ad(dtuple_check_typed(tuple));
+	ut_ad(index->page != FIL_NULL);
 
+	UNIV_MEM_INVALID(&cursor->up_match, sizeof cursor->up_match);
+	UNIV_MEM_INVALID(&cursor->up_bytes, sizeof cursor->up_bytes);
+	UNIV_MEM_INVALID(&cursor->low_match, sizeof cursor->low_match);
+	UNIV_MEM_INVALID(&cursor->low_bytes, sizeof cursor->low_bytes);
 #ifdef UNIV_DEBUG
 	cursor->up_match = ULINT_UNDEFINED;
 	cursor->low_match = ULINT_UNDEFINED;

storage/innodb_plugin/btr/btr0cur.c

@@ -393,7 +393,12 @@ btr_cur_search_to_nth_level(
 	ut_ad(dict_index_check_search_tuple(index, tuple));
 	ut_ad(!dict_index_is_ibuf(index) || ibuf_inside());
 	ut_ad(dtuple_check_typed(tuple));
+	ut_ad(index->page != FIL_NULL);
 
+	UNIV_MEM_INVALID(&cursor->up_match, sizeof cursor->up_match);
+	UNIV_MEM_INVALID(&cursor->up_bytes, sizeof cursor->up_bytes);
+	UNIV_MEM_INVALID(&cursor->low_match, sizeof cursor->low_match);
+	UNIV_MEM_INVALID(&cursor->low_bytes, sizeof cursor->low_bytes);
 #ifdef UNIV_DEBUG
 	cursor->up_match = ULINT_UNDEFINED;
 	cursor->low_match = ULINT_UNDEFINED;