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c894d97781b54fbf074677c9d67f81cd60a162ac
mariadb/sql/item_vers.h
Rex Johnston c894d97781 MDEV-41631 Check the class of the copy made by Item::shallow_copy() 
Item::shallow_copy() was meant to create a copy of the same class as the
item it is called on, but nothing enforced that. A class that does not
declare its own override inherits the one of its nearest concrete parent,
and get_item_copy<Parent>() then silently creates an object of the parent
class, losing the child's virtual behaviour (see MDEV-38801 for an earlier
instance with Item_cache_year).

Add the ITEM_SHALLOW_COPY(CLASS) macro, which declares the override, and
Item::dbug_check_shallow_copy_type(), a debug-only check called from
Query_arena::free_items() for every item freed. Once per dynamic type it
creates a shallow copy and asserts that it has the same typeid as the
original. Then, the copy is destroyed, which provides additional
coverage.

The check found these classes copied as their parent class, now fixed with
ITEM_SHALLOW_COPY():
  Item_join_operator_plus, Item_null_result, Item_old_field, Item_datetime,
  Item_empty_string, Item_return_int, Item_trigger_type_of_statement,
  in_string::Item_string_for_in_vector, Item_is_not_null_test,
  Item_interval_DDhhmmssff_typecast, Item_string_xml_non_const,
  Item_func_trt_trx_sees_eq, Item_field_refcursor (type_cursor plugin),
  Item_field_packable_scalar (type_assoc_array plugin).

These two classes do not support copying so the patch makes their
shallow_copy() to return NULL:
  Item_cache_wrapper, Item_sum_sp

Item_field_packable_row::shallow_copy() has assert(0). The patch makes
it return NULL.

This commit was prepared with help of Claude Code (Opus 5).
Sergei Petrunia added "delete item_copy" and did other minor edits.
2026-10-23 11:31:46 +03:00

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#ifndef ITEM_VERS_INCLUDED
#define ITEM_VERS_INCLUDED
/* Copyright (c) 2017, 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 Foundation; version 2 of the License.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA */
/* System Versioning items */
class Item_func_history: public Item_bool_func
{
public:
/*
@param a Item_field for row_end system field
*/
Item_func_history(THD *thd, Item *a): Item_bool_func(thd, a)
{
DBUG_ASSERT(a->type() == Item::FIELD_ITEM);
}
bool val_bool() override;
bool fix_length_and_dec(THD *thd) override
{
set_maybe_null();
null_value= 0;
decimals= 0;
max_length= 1;
return FALSE;
}
LEX_CSTRING func_name_cstring() const override
{
static LEX_CSTRING name= {STRING_WITH_LEN("is_history") };
return name;
}
void print(String *str, enum_query_type query_type) override;
protected:
Item *shallow_copy(THD *thd) const override
{ return get_item_copy<Item_func_history>(thd, this); }
};
class Item_func_trt_ts: public Item_datetimefunc
{
TR_table::field_id_t trt_field;
public:
Item_func_trt_ts(THD *thd, Item* a, TR_table::field_id_t _trt_field);
LEX_CSTRING func_name_cstring() const override
{
static LEX_CSTRING begin_name= {STRING_WITH_LEN("trt_begin_ts") };
static LEX_CSTRING commit_name= {STRING_WITH_LEN("trt_commit_ts") };
return (trt_field == TR_table::FLD_BEGIN_TS) ? begin_name : commit_name;
}
bool get_date(THD *thd, MYSQL_TIME *res, date_mode_t fuzzydate) override;
bool fix_length_and_dec(THD *thd) override
{ fix_attributes_datetime(decimals); return FALSE; }
protected:
Item *shallow_copy(THD *thd) const override
{ return get_item_copy<Item_func_trt_ts>(thd, this); }
};
class Item_func_trt_id : public Item_longlong_func
{
TR_table::field_id_t trt_field;
bool backwards;
longlong get_by_trx_id(ulonglong trx_id);
longlong get_by_commit_ts(MYSQL_TIME &commit_ts, bool backwards);
public:
Item_func_trt_id(THD *thd, Item* a, TR_table::field_id_t _trt_field, bool _backwards= false);
Item_func_trt_id(THD *thd, Item* a, Item* b, TR_table::field_id_t _trt_field);
LEX_CSTRING func_name_cstring() const override
{
static LEX_CSTRING trx_name= {STRING_WITH_LEN("trt_trx_id") };
static LEX_CSTRING commit_name= {STRING_WITH_LEN("trt_commit_id") };
static LEX_CSTRING iso_name= {STRING_WITH_LEN("trt_iso_level") };
switch (trt_field) {
case TR_table::FLD_TRX_ID:
return trx_name;
case TR_table::FLD_COMMIT_ID:
return commit_name;
case TR_table::FLD_ISO_LEVEL:
return iso_name;
default:
DBUG_ASSERT(0);
}
return NULL_clex_str;
}
bool fix_length_and_dec(THD *thd) override
{
bool res= Item_int_func::fix_length_and_dec(thd);
max_length= 20;
return res;
}
longlong val_int() override;
protected:
Item *shallow_copy(THD *thd) const override
{ return get_item_copy<Item_func_trt_id>(thd, this); }
};
class Item_func_trt_trx_sees : public Item_bool_func
{
protected:
bool accept_eq;
public:
Item_func_trt_trx_sees(THD *thd, Item* a, Item* b);
LEX_CSTRING func_name_cstring() const override
{
static LEX_CSTRING name= {STRING_WITH_LEN("trt_trx_sees") };
return name;
}
bool val_bool() override;
protected:
Item *shallow_copy(THD *thd) const override
{ return get_item_copy<Item_func_trt_trx_sees>(thd, this); }
};
class Item_func_trt_trx_sees_eq :
public Item_func_trt_trx_sees
{
public:
Item_func_trt_trx_sees_eq(THD *thd, Item* a, Item* b) :
Item_func_trt_trx_sees(thd, a, b)
{
accept_eq= true;
}
LEX_CSTRING func_name_cstring() const override
{
static LEX_CSTRING name= {STRING_WITH_LEN("trt_trx_sees_eq") };
return name;
}
protected:
ITEM_SHALLOW_COPY(Item_func_trt_trx_sees_eq)
};
#endif /* ITEM_VERS_INCLUDED */
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