Bug#42733: Type-punning warnings when compiling MySQL --

            strict aliasing violations.

One somewhat major source of strict-aliasing violations and
related warnings is the SQL_LIST structure. For example,
consider its member function `link_in_list` which takes
a pointer to pointer of type T (any type) as a pointer to
pointer to unsigned char. Dereferencing this pointer, which
is done to reset the next field, violates strict-aliasing
rules and might cause problems for surrounding code that
uses the next field of the object being added to the list.

The solution is to use templates to parametrize the SQL_LIST
structure in order to deference the pointers with compatible
types. As a side bonus, it becomes possible to remove quite
a few casts related to acessing data members of SQL_LIST.

sql/handler.h:
  Use the appropriate template type argument.
sql/item.cc:
  Remove now-unnecessary cast.
sql/item_subselect.cc:
  Remove now-unnecessary casts.
sql/item_sum.cc:
  Use the appropriate template type argument.
  Remove now-unnecessary cast.
sql/mysql_priv.h:
  Move SQL_LIST structure to sql_list.h
  Use the appropriate template type argument.
sql/sp.cc:
  Remove now-unnecessary casts.
sql/sql_delete.cc:
  Use the appropriate template type argument.
  Remove now-unnecessary casts.
sql/sql_derived.cc:
  Remove now-unnecessary casts.
sql/sql_lex.cc:
  Remove now-unnecessary casts.
sql/sql_lex.h:
  SQL_LIST now takes a template type argument which must
  match the type of the elements of the list. Use forward
  declaration when the type is not available, it is used
  in pointers anyway.
sql/sql_list.h:
  Rename SQL_LIST to SQL_I_List. The template parameter is
  the type of object that is stored in the list.
sql/sql_olap.cc:
  Remove now-unnecessary casts.
sql/sql_parse.cc:
  Remove now-unnecessary casts.
sql/sql_prepare.cc:
  Remove now-unnecessary casts.
sql/sql_select.cc:
  Remove now-unnecessary casts.
sql/sql_show.cc:
  Remove now-unnecessary casts.
sql/sql_table.cc:
  Remove now-unnecessary casts.
sql/sql_trigger.cc:
  Remove now-unnecessary casts.
sql/sql_union.cc:
  Remove now-unnecessary casts.
sql/sql_update.cc:
  Remove now-unnecessary casts.
sql/sql_view.cc:
  Remove now-unnecessary casts.
sql/sql_yacc.yy:
  Remove now-unnecessary casts.
storage/myisammrg/ha_myisammrg.cc:
  Remove now-unnecessary casts.

1 files changed, 28 insertions, 32 deletions

diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
index 6603aa55d03..c4963914036 100644
--- a/sql/sql_parse.cc
+++ b/sql/sql_parse.cc
@@ -1368,8 +1368,8 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
     mysql_reset_thd_for_next_command(thd);
 
     thd->lex->
-      select_lex.table_list.link_in_list((uchar*) &table_list,
-                                         (uchar**) &table_list.next_local);
+      select_lex.table_list.link_in_list(&table_list,
+                                         &table_list.next_local);
     thd->lex->add_to_query_tables(&table_list);
 
     /* switch on VIEW optimisation: do not fill temporary tables */
@@ -1845,7 +1845,7 @@ int prepare_schema_table(THD *thd, LEX *lex, Table_ident *table_ident,
   {
     DBUG_RETURN(1);
   }
-  TABLE_LIST *table_list= (TABLE_LIST*) select_lex->table_list.first;
+  TABLE_LIST *table_list= select_lex->table_list.first;
   table_list->schema_select_lex= schema_select_lex;
   table_list->schema_table_reformed= 1;
   DBUG_RETURN(0);
@@ -2041,7 +2041,7 @@ mysql_execute_command(THD *thd)
   /* first SELECT_LEX (have special meaning for many of non-SELECTcommands) */
   SELECT_LEX *select_lex= &lex->select_lex;
   /* first table of first SELECT_LEX */
-  TABLE_LIST *first_table= (TABLE_LIST*) select_lex->table_list.first;
+  TABLE_LIST *first_table= select_lex->table_list.first;
   /* list of all tables in query */
   TABLE_LIST *all_tables;
   /* most outer SELECT_LEX_UNIT of query */
@@ -2076,7 +2076,7 @@ mysql_execute_command(THD *thd)
   all_tables= lex->query_tables;
   /* set context for commands which do not use setup_tables */
   select_lex->
-    context.resolve_in_table_list_only((TABLE_LIST*)select_lex->
+    context.resolve_in_table_list_only(select_lex->
                                        table_list.first);
 
   /*
@@ -2417,7 +2417,7 @@ mysql_execute_command(THD *thd)
       goto error; /* purecov: inspected */
     thd->enable_slow_log= opt_log_slow_admin_statements;
     res = mysql_backup_table(thd, first_table);
-    select_lex->table_list.first= (uchar*) first_table;
+    select_lex->table_list.first= first_table;
     lex->query_tables=all_tables;
     break;
   }
@@ -2429,7 +2429,7 @@ mysql_execute_command(THD *thd)
       goto error; /* purecov: inspected */
     thd->enable_slow_log= opt_log_slow_admin_statements;
     res = mysql_restore_table(thd, first_table);
-    select_lex->table_list.first= (uchar*) first_table;
+    select_lex->table_list.first= first_table;
     lex->query_tables=all_tables;
     break;
   }
@@ -2723,7 +2723,7 @@ mysql_execute_command(THD *thd)
         if (create_info.used_fields & HA_CREATE_USED_UNION)
         {
           TABLE_LIST *tab;
-          for (tab= (TABLE_LIST*) create_info.merge_list.first;
+          for (tab= create_info.merge_list.first;
                tab;
                tab= tab->next_local)
           {
@@ -2893,7 +2893,6 @@ end_with_restore_list:
 	  check_access(thd,INSERT_ACL | CREATE_ACL,select_lex->db,&priv,0,0,
                        is_schema_db(select_lex->db))||
 	  check_merge_table_access(thd, first_table->db,
-				   (TABLE_LIST *)
 				   create_info.merge_list.first))
 	goto error;				/* purecov: inspected */
       if (check_grant(thd, priv_needed, all_tables, 0, UINT_MAX, 0))
@@ -3028,7 +3027,7 @@ end_with_restore_list:
       */
       res= write_bin_log(thd, TRUE, thd->query(), thd->query_length());
     }
-    select_lex->table_list.first= (uchar*) first_table;
+    select_lex->table_list.first= first_table;
     lex->query_tables=all_tables;
     break;
   }
@@ -3040,7 +3039,7 @@ end_with_restore_list:
       goto error; /* purecov: inspected */
     thd->enable_slow_log= opt_log_slow_admin_statements;
     res = mysql_check_table(thd, first_table, &lex->check_opt);
-    select_lex->table_list.first= (uchar*) first_table;
+    select_lex->table_list.first= first_table;
     lex->query_tables=all_tables;
     break;
   }
@@ -3060,7 +3059,7 @@ end_with_restore_list:
       */
       res= write_bin_log(thd, TRUE, thd->query(), thd->query_length());
     }
-    select_lex->table_list.first= (uchar*) first_table;
+    select_lex->table_list.first= first_table;
     lex->query_tables=all_tables;
     break;
   }
@@ -3083,7 +3082,7 @@ end_with_restore_list:
       */
       res= write_bin_log(thd, TRUE, thd->query(), thd->query_length());
     }
-    select_lex->table_list.first= (uchar*) first_table;
+    select_lex->table_list.first= first_table;
     lex->query_tables=all_tables;
     break;
   }
@@ -3101,7 +3100,7 @@ end_with_restore_list:
                                   lex->value_list,
                                   select_lex->where,
                                   select_lex->order_list.elements,
-                                  (ORDER *) select_lex->order_list.first,
+                                  select_lex->order_list.first,
                                   unit->select_limit_cnt,
                                   lex->duplicates, lex->ignore));
     /* mysql_update return 2 if we need to switch to multi-update */
@@ -3261,7 +3260,7 @@ end_with_restore_list:
     {
       /* Skip first table, which is the table we are inserting in */
       TABLE_LIST *second_table= first_table->next_local;
-      select_lex->table_list.first= (uchar*) second_table;
+      select_lex->table_list.first= second_table;
       select_lex->context.table_list= 
         select_lex->context.first_name_resolution_table= second_table;
       res= mysql_insert_select_prepare(thd);
@@ -3292,7 +3291,7 @@ end_with_restore_list:
         delete sel_result;
       }
       /* revert changes for SP */
-      select_lex->table_list.first= (uchar*) first_table;
+      select_lex->table_list.first= first_table;
     }
 
     /*
@@ -3354,8 +3353,7 @@ end_with_restore_list:
   case SQLCOM_DELETE_MULTI:
   {
     DBUG_ASSERT(first_table == all_tables && first_table != 0);
-    TABLE_LIST *aux_tables=
-      (TABLE_LIST *)thd->lex->auxiliary_table_list.first;
+    TABLE_LIST *aux_tables= thd->lex->auxiliary_table_list.first;
     multi_delete *del_result;
 
     if (!thd->locked_tables &&
@@ -5363,7 +5361,7 @@ static bool check_show_access(THD *thd, TABLE_LIST *table)
   case SCH_STATISTICS:
   {
     TABLE_LIST *dst_table;
-    dst_table= (TABLE_LIST *) table->schema_select_lex->table_list.first;
+    dst_table= table->schema_select_lex->table_list.first;
 
     DBUG_ASSERT(dst_table);
 
@@ -6062,7 +6060,7 @@ bool mysql_test_parse_for_slave(THD *thd, char *inBuf, uint length)
   mysql_reset_thd_for_next_command(thd);
 
   if (!parse_sql(thd, & parser_state, NULL) &&
-      all_tables_not_ok(thd,(TABLE_LIST*) lex->select_lex.table_list.first))
+      all_tables_not_ok(thd, lex->select_lex.table_list.first))
     error= 1;                  /* Ignore question */
   thd->end_statement();
   thd->cleanup_after_query();
@@ -6200,7 +6198,7 @@ add_proc_to_list(THD* thd, Item *item)
   *item_ptr= item;
   order->item=item_ptr;
   order->free_me=0;
-  thd->lex->proc_list.link_in_list((uchar*) order,(uchar**) &order->next);
+  thd->lex->proc_list.link_in_list(order, &order->next);
   return 0;
 }
 
@@ -6209,7 +6207,7 @@ add_proc_to_list(THD* thd, Item *item)
   save order by and tables in own lists.
 */
 
-bool add_to_list(THD *thd, SQL_LIST &list,Item *item,bool asc)
+bool add_to_list(THD *thd, SQL_I_List<ORDER> &list, Item *item,bool asc)
 {
   ORDER *order;
   DBUG_ENTER("add_to_list");
@@ -6221,7 +6219,7 @@ bool add_to_list(THD *thd, SQL_LIST &list,Item *item,bool asc)
   order->free_me=0;
   order->used=0;
   order->counter_used= 0;
-  list.link_in_list((uchar*) order,(uchar**) &order->next);
+  list.link_in_list(order, &order->next);
   DBUG_RETURN(0);
 }
 
@@ -6335,7 +6333,7 @@ TABLE_LIST *st_select_lex::add_table_to_list(THD *thd,
   /* check that used name is unique */
   if (lock_type != TL_IGNORE)
   {
-    TABLE_LIST *first_table= (TABLE_LIST*) table_list.first;
+    TABLE_LIST *first_table= table_list.first;
     if (lex->sql_command == SQLCOM_CREATE_VIEW)
       first_table= first_table ? first_table->next_local : NULL;
     for (TABLE_LIST *tables= first_table ;
@@ -6377,7 +6375,7 @@ TABLE_LIST *st_select_lex::add_table_to_list(THD *thd,
     previous table reference to 'ptr'. Here we also add one element to the
     list 'table_list'.
   */
-  table_list.link_in_list((uchar*) ptr, (uchar**) &ptr->next_local);
+  table_list.link_in_list(ptr, &ptr->next_local);
   ptr->next_name_resolution_table= NULL;
   /* Link table in global list (all used tables) */
   lex->add_to_query_tables(ptr);
@@ -6610,7 +6608,7 @@ void st_select_lex::set_lock_for_tables(thr_lock_type lock_type)
   DBUG_ENTER("set_lock_for_tables");
   DBUG_PRINT("enter", ("lock_type: %d  for_update: %d", lock_type,
 		       for_update));
-  for (TABLE_LIST *tables= (TABLE_LIST*) table_list.first;
+  for (TABLE_LIST *tables= table_list.first;
        tables;
        tables= tables->next_local)
   {
@@ -7302,8 +7300,7 @@ bool multi_update_precheck(THD *thd, TABLE_LIST *tables)
 bool multi_delete_precheck(THD *thd, TABLE_LIST *tables)
 {
   SELECT_LEX *select_lex= &thd->lex->select_lex;
-  TABLE_LIST *aux_tables=
-    (TABLE_LIST *)thd->lex->auxiliary_table_list.first;
+  TABLE_LIST *aux_tables= thd->lex->auxiliary_table_list.first;
   TABLE_LIST **save_query_tables_own_last= thd->lex->query_tables_own_last;
   DBUG_ENTER("multi_delete_precheck");
 
@@ -7349,13 +7346,13 @@ bool multi_delete_precheck(THD *thd, TABLE_LIST *tables)
 
 bool multi_delete_set_locks_and_link_aux_tables(LEX *lex)
 {
-  TABLE_LIST *tables= (TABLE_LIST*)lex->select_lex.table_list.first;
+  TABLE_LIST *tables= lex->select_lex.table_list.first;
   TABLE_LIST *target_tbl;
   DBUG_ENTER("multi_delete_set_locks_and_link_aux_tables");
 
   lex->table_count= 0;
 
-  for (target_tbl= (TABLE_LIST *)lex->auxiliary_table_list.first;
+  for (target_tbl= lex->auxiliary_table_list.first;
        target_tbl; target_tbl= target_tbl->next_local)
   {
     lex->table_count++;
@@ -7525,8 +7522,7 @@ bool create_table_precheck(THD *thd, TABLE_LIST *tables,
 		   &create_table->grant.privilege, 0, 0,
                    test(create_table->schema_table)) ||
       check_merge_table_access(thd, create_table->db,
-			       (TABLE_LIST *)
-			       lex->create_info.merge_list.first))
+                               lex->create_info.merge_list.first))
     goto err;
   if (want_priv != CREATE_TMP_ACL &&
       check_grant(thd, want_priv, create_table, 0, 1, 0))