MDEV-18239 ASAN use-after-poison in process_str_arg / ... /...

MDEV-18239 ASAN use-after-poison in process_str_arg / ... / mark_unsupported_func or unexpected ER_BAD_FIELD_ERROR upon ALTER TABLE

renaming columns in a CHECK constraint during ALTER TABLE
taints the original TABLE and requires m_need_reopen=1.

In this case, though, renaming was redundant, so just don't do it.

mysql-test/r/check_constraint_innodb.result

+create table t1 (a int, b smallint) engine=innodb;
+connect con1,localhost,root,,test;
+alter table t1 add constraint check (b < 8);
+alter table t1 modify column b int, algorithm=inplace;
+ERROR 0A000: ALGORITHM=INPLACE is not supported. Reason: Cannot change column type INPLACE. Try ALGORITHM=COPY
+connection default;
+alter table t1 add primary key (a);
+drop table t1;
+disconnect con1;

mysql-test/t/check_constraint_innodb.test

+--source include/have_innodb.inc
+
+#
+# MDEV-18239 ASAN use-after-poison in process_str_arg / ... / mark_unsupported_func or unexpected ER_BAD_FIELD_ERROR upon ALTER TABLE
+#
+create table t1 (a int, b smallint) engine=innodb;
+connect con1,localhost,root,,test;
+alter table t1 add constraint check (b < 8);
+error ER_ALTER_OPERATION_NOT_SUPPORTED_REASON;
+alter table t1 modify column b int, algorithm=inplace;
+connection default;
+alter table t1 add primary key (a);
+drop table t1;
+disconnect con1;

sql/sql_table.cc

@@ -8123,7 +8123,12 @@ mysql_prepare_alter_table(THD *thd, TABLE *table,
       }
       if (!drop)
       {
-        check->expr->walk(&Item::rename_fields_processor, 1, &column_rename_param);
+        if (alter_info->flags & Alter_info::ALTER_RENAME_COLUMN)
+        {
+          check->expr->walk(&Item::rename_fields_processor, 1,
+                            &column_rename_param);
+          table->m_needs_reopen= 1; // because new column name is on thd->mem_root
+        }
         new_constraint_list.push_back(check, thd->mem_root);
       }
     }