MDEV-22563 Segfault on duplicate free of Item_func_in::array

Same array instance in two Item_func_in instances. First Item_func_in
instance is freed on table close. Second one is freed on
cleanup_after_query().

get_copy() depends on copy ctor for copying an item and hence does
shallow copy for default copy ctor. Use build_clone() for deep copy of
Item_func_in.

mysql-test/main/alter_table.result

@@ -2559,3 +2559,38 @@ drop view v1;
 #
 # End of 10.3 tests
 #
+#
+# MDEV-22563 Segfault on duplicate free of Item_func_in::array
+#
+create or replace table person_principal (
+person_id bigint not null,
+insurant_id varchar(10) not null,
+principal_id bigint not null,
+principal_officer_id bigint not null,
+nursing_degree tinyint null,
+nursing_degree_valid_from date not null default cast(current_timestamp(6) as date),
+carma_user_id bigint not null,
+current_date_time timestamp(6) not null default current_timestamp(6) on update current_timestamp(6),
+constraint pk_person_principal primary key (person_id asc),
+constraint ck_person_principal_nursing_degree check (nursing_degree in (1,2,3,4,5)));
+Warnings:
+Warning	1280	Name 'pk_person_principal' ignored for PRIMARY key.
+create or replace table person_principal_hist (
+person_id bigint not null,
+insurant_id varchar(10) not null,
+principal_id bigint not null,
+principal_officer_id bigint not null,
+nursing_degree tinyint null,
+nursing_degree_valid_from date not null default cast(now() as date),
+carma_user_id bigint not null,
+orig_date_time datetime(6) not null,
+constraint pk_person_principal_hist primary key (person_id asc, orig_date_time asc),
+constraint ck_person_principal_hist_nursing_degree check (nursing_degree in (1,2,3,4,5)));
+Warnings:
+Warning	1280	Name 'pk_person_principal_hist' ignored for PRIMARY key.
+insert into person_principal (person_id, insurant_id, principal_id, principal_officer_id, nursing_degree, nursing_degree_valid_from, carma_user_id)
+values (1, 'A123456789', 5, 1, 1, '2018-05-06', 1);
+alter table person_principal add column if not exists date_mask tinyint null;
+update person_principal set date_mask = 0;
+alter table person_principal modify column date_mask tinyint not null;
+drop tables person_principal_hist, person_principal;

mysql-test/main/alter_table.test

@@ -2076,3 +2076,38 @@ drop view v1;
 --echo #
 --echo # End of 10.3 tests
 --echo #
+
+--echo #
+--echo # MDEV-22563 Segfault on duplicate free of Item_func_in::array
+--echo #
+create or replace table person_principal (
+  person_id bigint not null,
+  insurant_id varchar(10) not null,
+  principal_id bigint not null,
+  principal_officer_id bigint not null,
+  nursing_degree tinyint null,
+  nursing_degree_valid_from date not null default cast(current_timestamp(6) as date),
+  carma_user_id bigint not null,
+  current_date_time timestamp(6) not null default current_timestamp(6) on update current_timestamp(6),
+  constraint pk_person_principal primary key (person_id asc),
+  constraint ck_person_principal_nursing_degree check (nursing_degree in (1,2,3,4,5)));
+
+create or replace table person_principal_hist (
+  person_id bigint not null,
+  insurant_id varchar(10) not null,
+  principal_id bigint not null,
+  principal_officer_id bigint not null,
+  nursing_degree tinyint null,
+  nursing_degree_valid_from date not null default cast(now() as date),
+  carma_user_id bigint not null,
+  orig_date_time datetime(6) not null,
+  constraint pk_person_principal_hist primary key (person_id asc, orig_date_time asc),
+  constraint ck_person_principal_hist_nursing_degree check (nursing_degree in (1,2,3,4,5)));
+
+insert into person_principal (person_id, insurant_id, principal_id, principal_officer_id, nursing_degree, nursing_degree_valid_from, carma_user_id)
+values (1, 'A123456789', 5, 1, 1, '2018-05-06', 1);
+alter table person_principal add column if not exists date_mask tinyint null;
+update person_principal set date_mask = 0;
+alter table person_principal modify column date_mask tinyint not null;
+drop tables person_principal_hist, person_principal;
+

sql/field.cc

@@ -11396,7 +11396,7 @@ Virtual_column_info* Virtual_column_info::clone(THD *thd)
     return NULL;
   if (expr)
   {
-    dst->expr= expr->get_copy(thd);
+    dst->expr= expr->build_clone(thd);
     if (!dst->expr)
       return NULL;
   }

sql/item.h

@@ -1586,6 +1586,7 @@ class Item: public Value_source,
   virtual bool is_order_clause_position() const { return false; }
   /* cloning of constant items (0 if it is not const) */
   virtual Item *clone_item(THD *thd) { return 0; }
+  /* deep copy item */
   virtual Item* build_clone(THD *thd) { return get_copy(thd); }
   virtual cond_result eq_cmp_result() const { return COND_OK; }
   inline uint float_length(uint decimals_par) const
@@ -2031,6 +2032,10 @@ class Item: public Value_source,
   virtual bool check_index_dependence(void *arg) { return 0; }
   /*============== End of Item processor list ======================*/
 
+  /*
+    Does not guarantee deep copy (depends on copy ctor).
+    See build_clone() for deep copy.
+  */
   virtual Item *get_copy(THD *thd)=0;
 
   bool cache_const_expr_analyzer(uchar **arg);