Fix clang -Wunused-but-set-variable

storage/innobase/data/data0data.cc

 /*****************************************************************************
 
 Copyright (c) 1994, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, 2020, MariaDB Corporation.
+Copyright (c) 2017, 2022, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -575,7 +575,6 @@ dtuple_convert_big_rec(
 	dfield_t*	dfield;
 	dict_field_t*	ifield;
 	ulint		size;
-	ulint		n_fields;
 	ulint		local_prefix_len;
 
 	if (!dict_index_is_clust(index)) {
@@ -604,7 +603,7 @@ dtuple_convert_big_rec(
 	a variable-length field that yields the biggest savings when
 	stored externally */
 
-	n_fields = 0;
+	ut_d(ulint n_fields = 0);
 
 	while (page_zip_rec_needs_ext(rec_get_converted_size(index, entry,
 							     *n_ext),
@@ -700,9 +699,8 @@ dtuple_convert_big_rec(
 		dfield_set_data(dfield, data, local_len);
 		dfield_set_ext(dfield);
 
-		n_fields++;
 		(*n_ext)++;
-		ut_ad(n_fields < dtuple_get_n_fields(entry));
+		ut_ad(++n_fields < dtuple_get_n_fields(entry));
 
 		if (upd && !upd->is_modified(longest_i)) {
 

storage/innobase/gis/gis0rtree.cc

@@ -998,7 +998,7 @@ rtr_page_split_and_insert(
 	lock_prdt_t		new_prdt;
 	rec_t*			first_rec = NULL;
 	int			first_rec_group = 1;
-	ulint			n_iterations = 0;
+	IF_DBUG(bool iterated = false,);
 
 	if (!*heap) {
 		*heap = mem_heap_create(1024);
@@ -1207,7 +1207,7 @@ rtr_page_split_and_insert(
 	the page, and it'll need the second round split in this case.
 	We test this scenario here*/
 	DBUG_EXECUTE_IF("rtr_page_need_second_split",
-			if (n_iterations == 0) {
+			if (!iterated) {
 				rec = NULL;
 				goto after_insert; }
 	);
@@ -1272,7 +1272,7 @@ rtr_page_split_and_insert(
 		parent. */
 		rtr_clean_rtr_info(cursor->rtr_info, true);
 		cursor->rtr_info = NULL;
-		n_iterations++;
+		IF_DBUG(iterated=true,);
 
 		rec_t* i_rec = page_rec_get_next(page_get_infimum_rec(
 			buf_block_get_frame(block)));

storage/innobase/include/ut0lst.h

 /*****************************************************************************
 
 Copyright (c) 1995, 2015, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2019, MariaDB Corporation.
+Copyright (c) 2019, 2022, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -25,8 +25,7 @@ Created 9/10/1995 Heikki Tuuri
 Rewritten by Sunny Bains Dec 2011.
 ***********************************************************************/
 
-#ifndef ut0lst_h
-#define ut0lst_h
+#pragma once
 
 /* Do not include univ.i because univ.i includes this. */
 
@@ -474,17 +473,17 @@ template <typename List, class Functor>
 void ut_list_validate(const List& list, Functor& functor)
 {
 	ut_list_map(list, functor);
-
+#ifdef UNIV_DEBUG
 	/* Validate the list backwards. */
-	ulint		count = 0;
+	auto count = list.count;
 
 	for (typename List::elem_type* elem = list.end;
 	     elem != 0;
 	     elem = (elem->*list.node).prev) {
-		++count;
+		--count;
 	}
-
-	ut_a(count == list.count);
+	ut_ad(!count);
+#endif
 }
 
 /** Check the consistency of a doubly linked list.
@@ -494,23 +493,24 @@ template <typename List, class Functor>
 inline void ut_list_validate(const List& list, const Functor& functor)
 {
 	ut_list_map(list, functor);
-
+#ifdef UNIV_DEBUG
 	/* Validate the list backwards. */
-	ulint		count = 0;
+	auto count = list.count;
 
 	for (typename List::elem_type* elem = list.end;
 	     elem != 0;
 	     elem = (elem->*list.node).prev) {
-		++count;
+		--count;
 	}
 
-	ut_a(count == list.count);
+	ut_ad(!count);
+#endif
 }
 
 template <typename List>
 inline void ut_list_validate(const List& list)
 {
-	ut_list_validate(list, NullValidate());
+  ut_d(ut_list_validate(list, NullValidate()));
 }
 
 #ifdef UNIV_DEBUG
@@ -561,8 +561,3 @@ ut_list_move_to_front(
 		ut_list_prepend(list, elem);
 	}
 }
-
-#ifdef UNIV_DEBUG
-#endif
-
-#endif /* ut0lst.h */