BUG#21902059: "CREATE TEMPORARY TABLE SELECT ..." AND BIT(1)

               COLUMNS

ANALYSIS:
=========
A valgrind error is reported when CREATE TABLE .. SELECT
involving BIT columns triggers a column type redefinition.

In general the pack_flag is set for BIT columns in
'mysql_prepare_create_table()'. However, during the above
operation, redefined column types was handled after the
special handling for BIT columns and thus pack_flag ended
up not being set correctly triggering the valgrind error.

FIX:
====
The patch fixes this problem by setting pack_flag correctly
for BIT columns in the case of column type redefinition.

sql/sql_table.cc

@@ -3081,8 +3081,31 @@ mysql_prepare_create_table(THD *thd, HA_CREATE_INFO *create_info,
 	else
 	{
 	  /* Field redefined */
+
+          /*
+            If we are replacing a BIT field, revert the increment
+            of total_uneven_bit_length that was done above.
+          */
+          if (sql_field->sql_type == MYSQL_TYPE_BIT &&
+              file->ha_table_flags() & HA_CAN_BIT_FIELD)
+            total_uneven_bit_length-= sql_field->length & 7;
+
 	  sql_field->def=		dup_field->def;
 	  sql_field->sql_type=		dup_field->sql_type;
+
+          /*
+            If we are replacing a field with a BIT field, we need
+            to initialize pack_flag. Note that we do not need to
+            increment total_uneven_bit_length here as this dup_field
+            has already been processed.
+          */
+          if (sql_field->sql_type == MYSQL_TYPE_BIT)
+          {
+            sql_field->pack_flag= FIELDFLAG_NUMBER;
+            if (!(file->ha_table_flags() & HA_CAN_BIT_FIELD))
+              sql_field->pack_flag|= FIELDFLAG_TREAT_BIT_AS_CHAR;
+          }
+
 	  sql_field->charset=		(dup_field->charset ?
 					 dup_field->charset :
 					 create_info->default_table_charset);