Fixed memory leak with DEFAULT(f) on Geometry field

MDEV-21056  Assertion `global_status_var.global_memory_used == 0'
failed upon shutdown after query with DEFAULT on a geometry
field

mysql-test/r/gis.result

@@ -2283,5 +2283,12 @@ ERROR 22003: Cannot get geometry object from data you send to the GEOMETRY field
 drop table t1;
 SET timestamp=default;
 #
+# MDEV-21056 Memory leak after query with DEFAULT on a geometry field
+#
+CREATE TABLE t1 (f POINT DEFAULT ST_GEOMFROMTEXT('Point(0 0)'));
+SELECT ST_GEOMFROMTEXT('Point(1 1)') IN ( DEFAULT( `f` ), ST_GEOMFROMTEXT('Point(2 2)') ) AS x FROM t1;
+x
+DROP TABLE t1;
+#
 # End of 10.2 tests
 #

mysql-test/t/gis.test

@@ -1805,6 +1805,14 @@ alter table t1 add column i int;
 drop table t1;
 SET timestamp=default;
 
+--echo #
+--echo # MDEV-21056 Memory leak after query with DEFAULT on a geometry field
+--echo #
+
+CREATE TABLE t1 (f POINT DEFAULT ST_GEOMFROMTEXT('Point(0 0)'));
+SELECT ST_GEOMFROMTEXT('Point(1 1)') IN ( DEFAULT( `f` ), ST_GEOMFROMTEXT('Point(2 2)') ) AS x FROM t1;
+DROP TABLE t1;
+
 --echo #
 --echo # End of 10.2 tests
 --echo #

sql/field.cc

@@ -8857,7 +8857,7 @@ int Field_geom::store(const char *from, uint length, CHARSET_INFO *cs)
 
       my_error(ER_TRUNCATED_WRONG_VALUE_FOR_FIELD, MYF(0),
                Geometry::ci_collection[geom_type]->m_name.str,
-               wkt.c_ptr(), db, tab_name, field_name,
+               wkt.c_ptr_safe(), db, tab_name, field_name,
                (ulong) table->in_use->get_stmt_da()->
                current_row_for_warning());
 

sql/item.cc

@@ -8968,8 +8968,10 @@ bool Item_default_value::fix_fields(THD *thd, Item **items)
   }
   if (!(def_field= (Field*) thd->alloc(field_arg->field->size_of())))
     goto error;
+  cached_field= def_field;
   memcpy((void *)def_field, (void *)field_arg->field,
          field_arg->field->size_of());
+  def_field->reset_fields();
   // If non-constant default value expression
   if (def_field->default_value && def_field->default_value->flags)
   {
@@ -8997,6 +8999,12 @@ bool Item_default_value::fix_fields(THD *thd, Item **items)
   return TRUE;
 }
 
+void Item_default_value::cleanup()
+{
+  delete cached_field;                        // Free cached blob data
+  cached_field= 0;
+  Item_field::cleanup();
+}
 
 void Item_default_value::print(String *str, enum_query_type query_type)
 {

sql/item.h

@@ -5358,21 +5358,23 @@ class Item_default_value : public Item_field
   void calculate();
 public:
   Item *arg;
+  Field *cached_field;
   Item_default_value(THD *thd, Name_resolution_context *context_arg)
     :Item_field(thd, context_arg, (const char *)NULL, (const char *)NULL,
                (const char *)NULL),
-     arg(NULL) {}
+    arg(NULL), cached_field(NULL) {}
   Item_default_value(THD *thd, Name_resolution_context *context_arg, Item *a)
     :Item_field(thd, context_arg, (const char *)NULL, (const char *)NULL,
                 (const char *)NULL),
-     arg(a) {}
+    arg(a), cached_field(NULL) {}
   Item_default_value(THD *thd, Name_resolution_context *context_arg, Field *a)
     :Item_field(thd, context_arg, (const char *)NULL, (const char *)NULL,
                 (const char *)NULL),
-     arg(NULL) {}
+    arg(NULL),cached_field(NULL) {}
   enum Type type() const { return DEFAULT_VALUE_ITEM; }
   bool eq(const Item *item, bool binary_cmp) const;
   bool fix_fields(THD *, Item **);
+  void cleanup();
   void print(String *str, enum_query_type query_type);
   String *val_str(String *str);
   double val_real();